## **Core Concept**
The question requires knowledge of ophthalmology, specifically drugs used for dilating pupils during eye examinations. The key concept here is understanding the difference between mydriatics (pupil dilators) and cycloplegics (which also paralyze accommodation). The ideal drug for Mohan would dilate his pupils (mydriasis) without affecting his accommodation.

## **Why the Correct Answer is Right**
Tropicamide is a muscarinic receptor antagonist that acts as a mydriatic and cycloplegic but has a relatively short duration of action. However, among the given options, **Cyclopentolate** and **Atropine** are both cycloplegic mydriatics. **Phenylephrine** is a mydriatic but does not have cycloplegic effects. **Tropicamide** has less cycloplegic effect compared to cyclopentolate and atropine, making it suitable for procedures where cycloplegia is not desired or needs to be minimized.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Atropine has both mydriatic and cycloplegic effects, making it less ideal if the goal is to avoid paralyzing accommodation.
- **Option B:** Cyclopentolate has significant cycloplegic effects in addition to mydriasis, which might not be desirable for Mohan.
- **Option D:** Phenylephrine is a pure mydriatic without cycloplegic effects but is often used in combination with other drugs for a more effective dilation.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that for a diagnostic eye exam where cycloplegia needs to be avoided, **Tropicamide** is often preferred due to its shorter duration of cycloplegic effect compared to atropine or cyclopentolate. However, for thorough examinations, especially in younger patients, cycloplegic agents might still be necessary.

## **Correct Answer:** C. Tropicamide.