If mass of the fissionable material is less than the critical mass, then

Options

A. fission and chain reaction both are impossible
B. fission is possible but chain reaction is impossible
C. fission is impossible but chain reaction is possible
D. fission and chain reaction both are possible.

Answer

To solve the question, we need to understand the concepts of fission, critical mass, and chain reactions. Let's break it down step by step.

### Step-by-Step Solution:

1. **Understanding Fission**:
- Fission is the process where a heavy nucleus splits into two or more lighter nuclei, along with the release of energy and neutrons. This process can occur spontaneously or can be induced by the absorption of a neutron.

2. **Understanding Critical Mass**:
- Critical mass is defined as the minimum amount of fissile material needed to maintain a sustained nuclear chain reaction. If the mass of the fissionable material is below this critical mass, it cannot sustain a chain reaction.

3. **Analyzing the Given Condition**:
- The problem states that the mass of the fissionable material is less than the critical mass. This means that while individual fission events can still occur, there aren't enough fissile nuclei present to sustain a chain reaction.

4. **Conclusion**:
- Since the mass is less than the critical mass, fission can still take place (individual fission events can occur), but a chain reaction cannot be sustained. Therefore, the correct answer to the question is that fission is possible but chain reaction is impossible.

### Final Answer:
- Fission is possible but chain reaction is impossible.