A farmer plants a different crop in the same field in each of three years. In the fourth year, the farmer sows a leguminous crop and then ploughs it into the soil. The following year, the rotation begins once more. By the time the rotation begins again, which microorganisms will have increased in number? 1. denitrifying bacteria 2. nitrifying bacteria 3. nitrogen-fixing bacteria 4. decomposing bacteria
- A1, 2 and 3
- B1, 2 and 4
- C1, 3 and 4
- D2, 3 and 4