How many four-membered ring isomers are there of dichlorocyclobutane, \({{\text{C}}_{\text{4}}}{{\text{H}}_{\text{6}}}{\text{C}}{{\text{l}}_{\text{2}}}\)?

A.     3

B.     4

C.     5

D.     6

C

This question tested assessment statement 20.6.3. The question was poorly answered with 30% choosing A and 41% B. It was the most difficult question in the paper answered correctly by only 17%.