Read the following statements.

Statement A: RNAi takes place in all eukaryotic organisms as a method of cellular defense.

Statement B: RNAi involves silencing the expression of target m-RNA by formation of  dsRNA.

In light of the given statements, choose the correct answer from the options given below.

Statement A is true. RNAi is a widespread and highly conserved regulatory mechanism in many eukaryotes. Some organisms, particularly certain fungi and unicellular eukaryotes, lack the RNAi machinery found in animals and plants.

Statement B is true. RNA interference (RNAi) involves the silencing of mRNA (messenger RNA) due to complementary double-stranded RNA (dsRNA). In RNAi, small RNA molecules, such as small interfering RNAs (siRNAs) or microRNAs (miRNAs), bind to their complementary sequences in the target mRNA. This binding leads to the degradation of the mRNA or the inhibition of its translation, resulting in the down regulation of the corresponding gene's expression. RNAi is a fundamental cellular mechanism for gene regulation in many eukaryotic organisms and is widely used in molecular biology research to selectively silence specific genes.