 Okay, so the reason this one is confusing is because it's kind of a, kind of a trick question, although you should remember from our discussion from, you know, the other lecture about alkenes, but let's just go over it. It says the following compound has only one stereocenter. Why then does it have four stereocenres? So they even point out the stereocenter to you, so you don't have to even go look for it. So you're saying, of course, right, that, well, it only has one stereocenter, then it should only have two stereoisomers. But that's the case conventionally, I guess you should say. But in this case, we've got this alkene here. So if you recall, so alkenes are going to have those two stereoisomers themselves, right? So when we bond these two carbons together, we can have the H up there, unless you put the H. So of course this is not a very good bonding. Okay, so you can have that geometric isomer there, and of course you can have the other one, right, to where these guys are in the same spot. But the hydrogen and the methyl group are switched. So in this case, you have the two big groups on the same side, so this is the Z alkene, and this is the E alkene. Okay, and then there's your stereocenter. And so for this one, you can have the R and the S, right, so the R or the S. So that would give you two stereoisomers. And then here you're going to have the R or the S. So you got R, Z, and S, Z, and R, E, and S, E. That's what you've got the four different stereoisomers. So I don't know, let's draw what I'm going to figure out which one it is. So the hydrogen is already back, right? So the bromine is going to be one. So this one's carbon, hydrogen, hydrogen, carbon, hydrogen, hydrogen, carbon. So that's the same. So we got to go to the next one. This one's hydrogen, hydrogen, hydrogen. This one's carbon, carbon, hydrogen. So this one's going to be two. That's three. So if we go, that's counterclockwise. So that's S, right? So that's the S, the S, E. And then the R would be just switching these two. Let's do it up here. The R, like that. And so that one's going to be the R. And then if you switch them, that would be the S, C. Okay, so that's the answer to that question.