In which of the following `Delta G` decreases if there can be some intramolecular rearrangement ?

Options

A.
B.
C.
D.

Explanation

To determine in which cases the Gibbs free energy (ΔG) decreases due to intramolecular rearrangement, we need to analyze the stability of the carbocations formed in each option. The stability of carbocations is crucial because more stable carbocations correspond to a more favorable (lower) ΔG.

### Step-by-Step Solution:

1. **Identify the Carbocation Stability**:
- For each structure (A, B, C, D), identify the type of carbocation present (primary, secondary, or tertiary).

2. **Analyze Structure A**:
- Structure A has a primary carbocation. It can undergo a hydride shift to form a tertiary carbocation, which is more stable.
- **ΔG**: Decreases (more stable carbocation formed).

3. **Analyze Structure B**:
- Structure B has a secondary carbocation. It can undergo a methyl shift to form a tertiary carbocation.
- **ΔG**: Decreases (more stable carbocation formed).

4. **Analyze Structure C**:
- Structure C also has a primary carbocation. Similar to structure A, it can undergo a hydride shift to form a tertiary carbocation.
- **ΔG**: Decreases (more stable carbocation formed).

5. **Analyze Structure D**:
- Structure D has a stable carbocation that does not undergo any rearrangement. Since there is no change in structure, ΔG does not decrease.
- **ΔG**: Does not decrease (no rearrangement).

6. **Conclusion**:
- The structures where ΔG decreases due to intramolecular rearrangement are A, B, and C.

### Final Answer:
The correct options where ΔG decreases due to intramolecular rearrangement are **A, B, and C**.