An example of microbial biocontrol agents that can be introduced to control butterfly caterpillars is

• A

  Bacillus thuringiensis which produces a protoxin that is activated in the acidic pH of the insect gut

• B

  Bacteria trichoderma that is very common in the root ecosystem and is very effective against animal pathogen

• C

  Fungi Trichoderma that is very common in the root ecosystem and is very effective against plant pathogen

• D

  Bacillus thuringiensis which produces a protoxin that is activated in the alkaline pH of the insect gut