- A Rhizobium, a nitrogen-fixing root bacterium
- B Bacillus thuringiensis
- C Azotobacter, a free-living nitrogen fixer
- D Pseudomonas, a common soil bacterium
Correct answer: B. Bacillus thuringiensis
Explanation: Bacillus thuringiensis (Bt) produces cry proteins (delta endotoxins) that are toxic to caterpillars and other insect pests.
Concept context
Microorganisms in food, medicine, sewage treatment, biocontrol, and biofertilizers