Which carbon skeleton represents an ester?

O
A.)C-C-C-C-C-O-C-C
O
B.)C-C-C-C-C-C-C-O
O
C.)C-C-C-C-C-C-C
D.) C3/4 C3/4 C3/4 C3/4 C3/4 O3/4 C3/4 C3/4