The correct option is B Nematodes
Nematode-specific gene was introduced into tobacco plant via Agrobacterium vector. The introduced DNA produced both sense and antisense RNA which were complimentary to each other and formed dsRNA. This RNA interference caused silencing of nematode-specific mRNA and was lethal for the survival of nematode in tobacco root cells. Transgenic tobacco plants were nematode resistant due to RNA interference. Thus, the correct answer is option B.