In RNAi, genes are silenced using:

1. ss DNA     

2. ds DNA       

3. ds RNA   

4. ss RNA

(3) A nematode Meloidegyne incognitia intects the roots of tobacco plants which reduces the production of tobacco, It can be prevented by using RNA interference process, which is checked by silencing of specific mRNA due to a complementary dsRNA.
dsRNA binds and prevents the translation of MRNA (silencing).