The correct options are
B Pests
C Weeds
Biocontrol is the control of pests, diseases and weeds of crop plants using biological agents. These harmful pests reduce crop yield and have traditionally been controlled by pesticides and weedicides. These are chemicals which cause soil and water pollution, and also tend to accumulate in the food chain to cause biomagnification. Biocontrol involves control using living organisms instead of chemicals to reduce the burden on the environment and to make use of harmless means to combat pests.