RNA interference shows fascinating promise as a tool in molecular biology for genetic diseases and other conditions like cancer, cystic fibrosis, etc. The mode of action of RNAi is: 

• A. Cutting DNA at a specific site.
• B. Regulating gene expression by gene silencing at the stage of translation or by blocking its translation into protein.
• C. Transcribing DNA into RNA.
• D. Breaking hydrogen bonds between complementary pairs during DNA replication.

Answer: (B)