Which one of the following sentences correctly uses a comparative adjective?

AThis is the worse picture I've ever seen.
BAlicia is a gooder swimmer than Marilynn.
COf the three girls, Janet is the better speaker.
DGeorge has a bigger appetite than Harry.

Verified Answer :

The correct use of comparative is found in the following sentence: 
D. George has a bigger appetite than Harry.

Below, I will correct the other sentences:

A. This is the worst picture I've ever seen.
B. Alicia is a better swimmer than Marilynn.
C. Of the three girls, Janet is the best speaker.