Boundaries: Supplements — Worked example

- [Lecturer] Hello, test takers. Let's take a look at this question. If you wanna pause the video now and try it on your own, be my guest. Okay, now let's do it together. I'm gonna read the question and its stem. "Sodium is the sixth most abundant element in the Earth's crust, but it can only be found in minerals alongside other elements. Pure sodium, a soft metal so reactive that it explodes if contacted by blank can only be produced in a lab. Which choice completes the text so that it conforms to the conventions of Standard English?" Remember that conventions of standard English is how the SAT refers to grammar. So the question is, which grammar convention are we testing here? And we can suss that out by looking at the choices, which are all the word water followed by different punctuation marks. Or the case of choice B, no punctuation mark at all, right? All of these are cording off this descriptive phrase about sodium, right? Pure sodium, comma, a soft metal so reactive that it explodes if contacted by water, punctuation or not can only be produced in a lab. So we're looking at this descriptive aside in the middle of a sentence. Another term for that is a supplement. Supplements are words, phrases, or clauses that add extra information to a sentence. Supplements are either essential or non-essential. Essential supplements do not need punctuation as they are essential to the meaning of the sentence. For example, take the sentence, "Plastics that contain BPA are potentially harmful." If you strip out the supplement, that contain BPA, the sentence no longer means the same thing. It would read, "Plastics are potentially harmful." That implies all plastics are potentially harmful which is not what the original sentence is saying. In other words, essential supplements provide information that the sentence needs to specify what it's talking about. Non essential supplements provide extra information that is not essential to the meaning of the sentence. Maybe you call these parentheticals or aside, different words for the same concept. They do need to be separated from the rest of the sentence with punctuation, which signals to the reader that the basic meaning of the sentence would be the same even without the supplement. Note how the supplement in this example is set off by paired commas. "Jackson, who was daydreaming, failed to notice the treasure chest." Now if we zap out the comma bounded part we get, "Jackson failed to notice the treasure chest." The meaning of the sentence has not changed. We've lost some extra detail about Jackson, but we still know who we're talking about. The punctuation that surrounds this supplement could have just as easily been dashes or parentheses, but whatever they are, they have to match one another. And if a supplement begins or ends a sentence it only needs one punctuation mark to separate it from the rest of the sentence. Here's a simple way of determining whether a supplement is essential or non-essential. It's essential if it specifies who or what we're talking about, and it's non-essential if we know who or what we're talking about without it. Basically essential equals part of the noun itself while non-essential equals extra information about the noun, but not part of the noun. Your job in these questions is to determine what kind of punctuation, if any, is needed to set off the supplement in the target sentence. Once we identify that we're punctuating a supplemental description, we can look at the rest of the sentence to see how the rest of the supplement is punctuated. Let's talk through how this strategy works. So the first thing to do in these questions is identify the supplement, where it begins and ends and whether it's essential or non-essential. If it's essential, it gets no punctuation marks. Nothing before and nothing after. If it's not essential, move on to step three. Where does the non-essential supplement appear in the sentence? If it's at the start, use a comma. If it's at the end, use a comma or rarely a dash. If it's in the middle of the sentence then you'll need a pair of punctuation marks to separate it from the rest of the sentence. Sometimes the text will give you one of the pair of punctuation marks needed. If so, you should match that punctuation mark on the other end of the supplement. That's it. It can be easy to get into the weeds with this sort of question. But if we focus down on finding the supplement, it falls into place. Okay, so back to the question. The first thing I wanna do is find the supplement. What is the descriptive phrase and what's being described in that second sentence? Okay, so pure sodium is the thing being described as "a soft metal so reactive that explodes if contacted by water", right? So from a soft metal to water, the end of the blank, is our supplement. We know it's not essential because we already have this comma right here. In fact, let me clean this up a little bit. We have that comma right before it and an essential supplement wouldn't have a comma before or after, but we can double check this by taking it out of the sentence. Pure sodium can only be produced in a lab. That still makes sense and is clear, which confirms that the supplement is definitely non-essential. And since it comes in the middle of a sentence we need punctuation on both sides to set it off. And again, we already have that comma there, starred at the beginning of the phrase, which means that our answer is the only other comma, A. Let me pull back and explain a little. Our punctuation options are comma, no punctuation, dash, semicolon, and we want to match the punctuation used at the beginning of the supplement. Think of it like parenthesis. You can't just start an open parenthesis without closing it off. That's ungrammatical. You have to close it. Because this supplement starts off with a comma, we want to match it with a comma. If the punctuation after sodium were a dash we use a dash to match it. The semicolon is wrong here because there isn't an independent clause on either side of it. With semicolons, remember to use the before and after test. If there isn't an independent clause on both sides of the semicolon, you can't use it. So our answer is A. Let's talk through some top tips for questions like these. Match the punctuation. If you see a comma, match it with a comma. If you see a parenthesis, match it with a parenthesis. If you see a dash, match it with a dash. You will see items that don't involve paired punctuation marks where the sentence supplement comes at the beginning or the end of the sentence, and that'll just require either a comma or a dash. You will never be required to choose between two equally good options in those questions. Top tip number two, mind your that's and whishes. Relative clauses that begin with that almost always carry essential information and generally aren't punctuated. As in, "The boat that sailed to Tobago was built by my father." Whereas which clauses are always set off by commas because they generally carry extra info that isn't essential to the core meaning of the sentence. As in, "The boat, which sailed to Tobago, was built by my father." Note that both of these sentences are grammatically correct. The first one makes clear what boat was built by my father and the second one uses the Tobago voyage as a non-essential aside. The first sentence suggests that there might be several boats we're considering, but that this specific one built by my father was the one that sailed to Tobago. Whereas the second one, we're just adding a detail about the one boat that is the subject of the statement. You see the difference? All right. Good luck out there, test takers. You've got this.