## PrepTest 79, Game 4, Question 19

### Transcript

Question number 19 is a global question asking, which one of the following could be the computer that was infected from outside the network? So, in other words, which computer could be at the very beginning of a virus chain? Now let's start using our rules to eliminate answers. I think the easiest rule to use right now is rule number 3. We know that R and S have to get the virus from someone else.

So what does that mean? Well, that means they can't be the one that kicks off the whole infection chain. They can't be getting it from outside the network because they have to get it from someone else who's in the network. That's why R is not correct and S is not correct. Then you can take a look at rules 4 and 5.

You know that Q has to get the virus from either R or T. So Q can't be the one that gets the virus first, and P can't get the virus first either because P has to get the virus from T or from U. So that gets rid of answer choice A. The correct answer through process of elimination is gonna be E. Now if you're curious about why T could be the first, we could go ahead and try it out.

So let's see, could we have T go to P to satisfy rule number 5, T can go to P. Let's have P go to both R and S. That's gonna satisfy rule number 3. Let's have the R go to Q. That's gonna satisfy rule number 4. And then let's have the S go to U.

That's gonna satisfy rule number 2. So here we proven that T could be the first computer that gets the virus.