Semi-conservative DNA replication means that one stand is new DNA and the other contains a newly synthesized strand.
Random changes in allele frequency in a population are usually called genetic drift. The reason why this is the answer is because it is a very specific word which is used to describe exactly that - random changes in allele frequency.
All the other cases; answers, here aren't correct and don't apply.
I think the answer will be C
Answer:
The expression of the mRNA decreases.
Explanation:
The RNAi binds to some proteins forming a silencing complex. This complex binds to the target mRNA (of which the RNAi is complementary) and cleaves it (cuts it). The cell will detect the generated fragments of mRNA , recognize they are aberrant and will thus degrade them.
All in all, this mechanism silences (reduces) the expression of the mRNA, because it will be degraded instead of translated into protein.