RNAi methodology uses double-stranded pieces of RNA to trigger a breakdown or blocking of mRNA. For which of the following might it more possibly be useful?

A) to raise the rate of production of a needed digestive enzyme
B) to decrease the production from a harmful gain-of-function mutated gene
C) to destroy an unwanted allele in a homozygous individual
D) to form a knockout organism that will not pass the deleted sequence to its progeny
E) to raise the concentration of a desired protein