To determine which compound can have a meso form, we need to understand the concept of meso compounds. Meso compounds are those that have multiple stereocenters but possess an internal plane of symmetry, making them achiral.
### Step-by-Step Solution:
1. **Understand Meso Compounds**:
- Meso compounds have multiple stereocenters and an internal plane of symmetry. This means that one half of the molecule is a mirror image of the other half.
2. **Analyze Each Option**:
- We are given four options. We need to analyze each structure to check for the presence of an internal plane of symmetry.
3. **Option A**:
- The structure has different groups attached to the stereocenters (e.g., CH3, C2H5, OH, CN).
- When we try to draw a plane of symmetry, we find that CH3 does not match with C2H5, indicating no internal plane of symmetry.
- **Conclusion**: Not a meso compound.
4. **Option B**:
- The structure has CH3, OH, and hydrogen groups arranged such that there are two identical CH3 groups on either side.
- When we draw a plane of symmetry, CH3 reflects onto CH3, OH reflects onto OH, and hydrogen reflects onto hydrogen.
- **Conclusion**: This compound has an internal plane of symmetry, making it a meso compound.
5. **Option C**:
- The structure has C2H5, OH, and CH3 groups.
- The C2H5 group does not have a corresponding group on the other side to reflect onto, indicating no internal plane of symmetry.
- **Conclusion**: Not a meso compound.
6. **Option D**:
- The structure has OH, CH2, CH, and CH3 groups.
- Similar to previous options, the groups do not match up across a potential plane of symmetry.
- **Conclusion**: Not a meso compound.
7. **Final Conclusion**:
- The only compound that has a meso form is **Option B**.
