Which Base-Pairing System is Correct

Question

Which base-pairing system is correct?  
A) A to G; T to C
B) A to T; G to C
C) A to C; G to T
D) A to T or C; G to C or A
E) A to T or G; G to C or A

Accepted Answer

A always pairs with T and G always pairs with C. This base-pairing system is known as complementary base pairing. Choice B is the only option that represents complementary base pairing.