Which of the following options includes biofertilisers ?

Options

A. Cowdung manure and farmyard waste
B. A quick growing crop ploughed back into the field
C. Nostoc, Oscillatoria
D. All of these

Explanation

To determine which of the following options includes biofertilizers, we need to analyze each option based on the definition of biofertilizers. Biofertilizers are substances that contain living microorganisms which promote plant growth by increasing the availability of nutrients in the soil.

### Step-by-Step Solution:

1. **Understand the Definition of Biofertilizers**:
- Biofertilizers are derived from living microorganisms that enhance soil fertility and nutrient content without causing environmental harm.

2. **Analyze Option A: Cow dung manure and farm yard waste**:
- Cow dung and farm yard waste are organic fertilizers, but they are not derived from specific microorganisms. Therefore, this option does not qualify as a biofertilizer.

3. **Analyze Option B: Quick growing crop plot brought back into the field**:
- This option refers to green manure, which is also not derived from specific microorganisms. Thus, it does not qualify as a biofertilizer.

4. **Analyze Option C: Nostoc and Oscillatoria**:
- Nostoc and Oscillatoria are types of cyanobacteria. They are capable of fixing nitrogen from the atmosphere and adding organic matter to the soil. This makes them valid examples of biofertilizers.

5. **Analyze Option D: All of these**:
- Since options A and B do not qualify as biofertilizers, option D cannot be correct.

6. **Conclusion**:
- The correct answer is **Option C: Nostoc and Oscillatoria**, as they are the only ones that fit the definition of biofertilizers.

### Final Answer:
**Option C: Nostoc and Oscillatoria**