Answer: Lactobacillus.
- A Lactobacillus
- B Rhizobium
- C Penicillium
- D Aspergillus
Correct answer: A. Lactobacillus
Explanation: Lactobacillus bacteria ferment milk sugar into lactic acid, forming curd.
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