The bases of rna are the same as those of dna except that rna has

uracil instead of thymine.

uracil instead of adenine

cytosine instead of guanine.

cysteine instead of cytosine

It is A. uracil instead of thymine. This is because though they are practically identical, but RNA has ribose sugar, as opposed to deoxyribose sugar in DNA and RNA has a uracil base instead of thymine.

the correct answer is:

a population changes in response to a change in the environment.