Answer: The alkaline pH of the insect gut.
- A The acidic pH of the human stomach
- B Exposure to sunlight on leaves
- C The alkaline pH of the insect gut
- D The anaerobic conditions in soil
Correct answer: C. The alkaline pH of the insect gut
Explanation: The crystal protein is an inactive protoxin that is solubilised and activated by the alkaline pH of the insect gut, after which it damages the gut epithelium and kills the larva.
Sewage passes through physical removal (primary), then aerobic biological treatment where microbes form flocs that consume organic matter (secondary); the settled activated sludge is then digested anaerobically to produce biogas - a deliberate switch from aerobic to anaerobic conditions between stages.
Concept context
Microorganisms in food, medicine, sewage treatment, biocontrol, and biofertilizers