Correct answer is option (A) i.e Trichoderma sp. against certain plants pathogens
A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma species are free living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens. Nucleopolyhedrovirus are also used as biocontrol agent but not against white rust of Brassica.