**Core Concept**
Anti-muscarinic drugs, also known as anticholinergics, block the action of acetylcholine at muscarinic receptors in the central and peripheral nervous system. They are used to treat various conditions such as Parkinson's disease, incontinence, and gastrointestinal disorders. However, their use can be problematic in certain conditions where the parasympathetic nervous system plays a crucial role in maintaining homeostasis.

**Why the Correct Answer is Right**
In conditions like angle-closure glaucoma, the parasympathetic nervous system helps to constrict the pupil and increase aqueous outflow, thereby reducing intraocular pressure. Anti-muscarinic drugs can block this parasympathetic effect, leading to pupil dilation and increased intraocular pressure, which can exacerbate the condition. This is because the parasympathetic nervous system's role is crucial in maintaining a patent pupil and reducing intraocular pressure, and blocking this effect can worsen the condition.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because anti-muscarinic drugs are not typically contraindicated in asthma. In fact, ipratropium bromide, an anti-muscarinic drug, is used as a bronchodilator in asthma.
**Option B:** This option is incorrect because anti-muscarinic drugs are not typically contraindicated in urinary retention. In fact, oxybutynin, an anti-muscarinic drug, is used to treat urinary incontinence.
**Option C:** This option is incorrect because anti-muscarinic drugs are not typically contraindicated in gastroesophageal reflux disease (GERD). In fact, some anti-muscarinic drugs, such as dicyclomine, are used to treat GERD.

**Clinical Pearl / High-Yield Fact**
Anti-muscarinic drugs can precipitate angle-closure glaucoma by blocking the parasympathetic effect on the iris sphincter muscle, leading to pupil dilation and increased intraocular pressure. It's essential to avoid these drugs in patients with a history of angle-closure glaucoma.

**Correct Answer: C. Angle-closure glaucoma**