**Core Concept**
Mydriatic drugs are used to dilate the pupils for various medical and surgical procedures. They work by either stimulating the muscarinic receptors in the ciliary muscles or by blocking the muscarinic receptors in the radial and circular muscles of the iris.

**Why the Correct Answer is Right**
The correct answer is **Tropicamide**. Tropicamide is a non-selective muscarinic receptor antagonist that causes rapid and short-lasting mydriasis. It is commonly used in ophthalmology to dilate pupils for examination of the retina and other intraocular structures. Tropicamide works by blocking the action of acetylcholine on muscarinic receptors in the iris sphincter muscle, leading to relaxation of the muscle and dilation of the pupil. Its short duration of action makes it ideal for diagnostic purposes.

**Why Each Wrong Option is Incorrect**
* **Option A:** **Atropine** has a longer duration of action compared to Tropicamide, making it less suitable for short-term mydriasis.
* **Option B:** **Cyclopentolate** is another muscarinic receptor antagonist, but it has a longer duration of action than Tropicamide and is often used for longer-term mydriasis.
* **Option D:** **Pilocarpine** is a muscarinic receptor agonist that causes miosis (pupil constriction), making it the opposite of a mydriatic drug.

**Clinical Pearl / High-Yield Fact**
It is essential to note that mydriatic drugs can cause complications such as angle closure glaucoma, especially in patients with pre-existing narrow angles. Therefore, it is crucial to use these drugs judiciously and with caution.

**Correct Answer: C. Cyclopentolate. Cyclopentolate is a muscarinic receptor antagonist that causes mydriasis.**