Which of the following groups exerts `+m` effect when attached with benzene ring?

Options

A. `-overset(o+)(S)(CH_(3))_(2)"group"`
B. `-overset(o+)(N)(CH_(3))_(3)"group"`
C. `-OCH_(3)"group"`
D. `-NHCH_(3)"group"`

Explanation

To determine which of the given groups exerts a +M (mesomeric) effect when attached to a benzene ring, we need to analyze each option based on the presence of lone pairs of electrons and their ability to donate electron density to the benzene ring. The +M effect increases the electron density at the ortho and para positions of the benzene ring.

### Step-by-Step Solution:

1. **Understanding +M Effect**:
- The +M effect refers to the mesomeric effect, where groups with lone pairs of electrons can donate electron density to the benzene ring, enhancing its reactivity at the ortho and para positions.

2. **Analyzing Option A**:
- The first option contains a sulfur atom with a positive charge (S^+).
- Since sulfur has a positive charge, it means that its lone pair of electrons has already been donated, and thus it cannot donate any more electron density to the benzene ring.
- **Conclusion**: Option A does not exert a +M effect.

3. **Analyzing Option B**:
- The second option features a nitrogen atom (N) with a positive charge (N^+).
- Similar to sulfur in Option A, the nitrogen with a positive charge does not have a lone pair available to donate to the benzene ring.
- **Conclusion**: Option B does not exert a +M effect.

4. **Analyzing Option C**:
- The third option is OCH3 (methoxy group).
- Oxygen has a lone pair of electrons that can be donated to the benzene ring. This donation increases the electron density at the ortho and para positions.
- **Conclusion**: Option C exerts a +M effect.

5. **Analyzing Option D**:
- The fourth option is NHCH3 (aniline derivative).
- The nitrogen atom in this group has a lone pair of electrons that can also be donated to the benzene ring, enhancing the electron density at the ortho and para positions.
- **Conclusion**: Option D exerts a +M effect.

6. **Final Result**:
- The groups that exert a +M effect when attached to the benzene ring are **Option C (OCH3)** and **Option D (NHCH3)**.