Which two molecules are cis-trans isomers of each other?

A.     X and Z

B.     X and Y

C.     W and Y

D.     W and Z

A

One respondent stated that this question was difficult. However, the question was in the midrange of difficulty and in fact was the ${\text{1}}{{\text{4}}^{{\text{th}}}}$ easiest question on the paper with 77.42% of candidates getting the correct answer, A. The question had a linked discrimination index of 0.40.