The `E`-isomer among the following is:

Options

A.
B.
C.
D.

Explanation

To determine the `E`-isomer among the given options, we will follow these steps:

### Step 1: Understand the Definition of E-Isomer
The `E`-isomer is characterized by having the higher priority substituents on the double-bonded carbons positioned on opposite sides. In contrast, if the higher priority groups are on the same side, it is termed the `Z`-isomer.

### Step 2: Identify the Structures
We are given multiple structures. We will analyze each structure to determine the priority of the substituents on either side of the double bond.

### Step 3: Analyze Each Option
1. **Option 1**:
- Structure: C=C with Cl, CH3 on one side and Br, C2H5 on the other.
- Priority: Cl (higher atomic number) > CH3 and Br > C2H5.
- Result: Both higher priority groups (Cl and Br) are on the same side → **Z-isomer**.

2. **Option 2**:
- Structure: C=C with Cl, CH3 on one side and C2H5, CHO on the other.
- Priority: Cl > CH3 and C2H5 > CHO (since O has a higher atomic number).
- Result: Higher priority groups (Cl and C2H5) are on opposite sides → **E-isomer**.

3. **Option 3**:
- Structure: C=C with CH3, CH2 on one side and CH3, H on the other.
- Priority: CH3 > CH2 and CH3 > H.
- Result: Higher priority groups (CH3 and CH3) are on the same side → **Z-isomer**.

4. **Option 4**:
- Structure: C=C with CHCl2, H on one side and CH3, H on the other.
- Priority: CHCl2 > H and CH3 > H.
- Result: Higher priority groups (CHCl2 and CH3) are on opposite sides → **E-isomer**.

### Step 4: Conclusion
From the analysis, we find that:
- Option 2 is an `E`-isomer.
- Option 4 is also an `E`-isomer.

However, since the question asks for the `E`-isomer among the options and typically only one is expected, we conclude that **Option 2** is the correct answer.

### Final Answer:
**The `E`-isomer among the following is Option 2.**

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