Answer:
A
Step-by-step explanation:
in DNA there is complementary base pairing which is that Adenine always pairs with Thymine and Cytosine always pairs with Guanine. therefore, if there is a certain amount of adenine in the DNA it must have the same amount of its complementary base, thymine.
the answer cannot be b as cytosine and thymine are not complementary base pairs. although b can coincidently be correct- that the amount of cytosine and thymine are equal- the question states that it must always be true. the answer cannot be c as ribose is found in RNA and deoxribose is found in DNA.