Which of the following compound will show tautomerism?

Options

A.
B. `Me_3C--C-=N`
C.
D.

Explanation

To determine which of the given compounds will show tautomerism, we need to understand the concept of tautomerism and analyze each compound based on the presence of alpha-hydrogens and the ability to form enol forms.

### Step-by-Step Solution:

1. **Understanding Tautomerism**:
- Tautomerism is a type of isomerism where two isomers, called tautomers, can readily interconvert. This typically involves the relocation of a hydrogen atom and a shift of a double bond. The most common example is the keto-enol tautomerism, where a ketone (or aldehyde) can convert to its corresponding enol form.

2. **Identifying Alpha-Hydrogens**:
- For a compound to exhibit tautomerism, it must have at least one alpha-hydrogen (a hydrogen atom attached to the carbon adjacent to the carbonyl carbon). The presence of this hydrogen is crucial for the tautomerization process.

3. **Analyzing Each Compound**:
- **Compound A**:
- Structure: Contains a carbonyl group (C=O) and has alpha-hydrogens available for removal.
- Conclusion: This compound can undergo tautomerism.

- **Compound B**:
- Structure: Contains a carbon with a triple bond and no alpha-hydrogens.
- Conclusion: This compound cannot undergo tautomerism due to the absence of alpha-hydrogens.

- **Compound C**:
- Structure: A bicyclic compound with a carbonyl group and limited alpha-hydrogens.
- Conclusion: Although it has one alpha-hydrogen, the non-planarity of the structure prevents it from effectively undergoing tautomerism.

- **Compound D**:
- Structure: Similar to compound A but lacks conjugation and has no effective way to stabilize the enol form.
- Conclusion: This compound cannot undergo tautomerism due to the lack of conjugation and instability of the enol form.

4. **Final Conclusion**:
- The only compound that shows tautomerism is **Compound A**.

### Answer:
The compound that will show tautomerism is **Compound A**.