$\begin {array} {1 1} (A)\;\text{Adenine and guanine; thymine and cystosine}\\ (B)\;\text{Uracil and adenine; cystosine and guanine} \\ (C)\;\text{Adenine and thymine; cystosine and guanine}\\ (D)\;\text{Adenine and thymine; guanine and uracil} \end {array}$
