Past questions can be useful on cannot be true questions. Any past diagram that works can prove an answer could be true. Could be true answers are wrong.

The diagram from question 14 proves that R and S can both test J. **A** is wrong.

The diagram from question 17 shows that R and T can both test J. It also shows that R and Y can test G. So **B** and **C** are wrong.

**D** is **CORRECT.** Seamus’ second day always has to come after Y’s first day. So Seamus could only test G with T on his first day.

That means T goes in the first day of H. Y and S have to test F, since Y can’t test J.

There’s no way to fit Y’s other test and both of R’s tests in the remaining spots, since Y can’t test J. If you have Y test H on the second day, R is forced to test J both days, which isn’t allowed.

This diagram shows that T and Y could both test F, so **E** is wrong.

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Although your analysis for Q 18 is correct, your diagram demonstrating how (E) could be true and is thus incorrect is wrong because it doesn’t place both T and Y in F as answer choice (E) states. Instead, your diagram proves how answer choice (B), Both R and T test J, could be true- which we already eliminated by looking at Q 17’s hypothetical for (B).

Thanks! I mixed up diagrams. I’ve just made a new diagram and edited the explanation. Should be correct now.