Which of these bases form a true complementary pair?

cytosine and thymine

adenine and guanine

cytosine and guanine

thymine and uracil

cytosine and guanine

Explanation:

First choice and second choice is incorrect because look at our answer. (Cytosine pairs with Guanine, and thymine pairs with Adenine)

Fourth is incorrect because thymine pairs with Adenine (and in RNA Uracil pairs with Adenine)

Cytosine and guanine,

The way I remember is cars in the garage (cytosine and guanine) and apples on the trees (adenine and thymine)