Seven students A, B, C, D, E, F and G take a series of tests. No two students get similar marks. G always scores more than A. A always scores more than B. Each time either C scores the highest and E gets the least, or alternatively D scores the highest and F or B scores the least. If G is ranked fifth, which of these must be true?

A

C is ranked second

B

D scores the highest

C

E is ranked third

D

B is ranked fourth