12. Which of the following statements correctly distinguishes the mode of gene silencing by microRNA versus RNAi? (A) microRNA almost always leads to slicing of mRNA, whereas RNAi does not (B) RNAi is typically associated with perfect complementarity, whereas microRNA often represses translation through imperfect pairing (C) RNAi uses Dicer but microRNA does not (D) RNAi functions only in the nucleus