The correct option is (a) Fungicides
For explanation I would say: Fungicides are used against fungus, to control the growth of fungus, the protectant category of the fungicides is used to prevent germination of fungal spores by forming a surface deposit on foliage, insecticides are used to kill insects, Nematicides are generally used to kill and control the population of nematodes in various places like houses, acaricides is used to control the population of mites.