**Core Concept**
The question tests the understanding of **beta blockers** and their effects on **glaucoma**. Beta blockers can have various systemic and local effects, including on the eye. In the context of glaucoma, the intraocular pressure (IOP) is a critical factor.

**Why the Correct Answer is Right**
Beta blockers that are non-selective, such as **propranolol** and **timolol** (when used systemically), can worsen glaucoma by potentially decreasing the outflow of aqueous humor, thereby increasing IOP. However, **timolol** is actually used topically to treat glaucoma by reducing aqueous humor production. The key is the route of administration and the specific beta blocker used.

**Why Each Wrong Option is Incorrect**
**Option A:** Without specific options, it's challenging to provide detailed incorrect reasoning. However, typically, beta blockers like **atenolol** or **nadolol** are not directly implicated in worsening glaucoma when used systemically for cardiovascular indications, but their use needs caution.
**Option B:** Similarly, without specifics, it's hard to comment, but **betaxolol** is a selective beta-1 blocker used topically for glaucoma, suggesting its use is not to be avoided in glaucoma.
**Option C and D:** These would depend on the specific beta blockers listed, but in general, systemic use of non-selective beta blockers could be of concern in glaucoma patients.

**Clinical Pearl / High-Yield Fact**
A critical point to remember is that while systemic beta blockers can have adverse effects on glaucoma, topical beta blockers like **timolol** are actually a mainstay in the treatment of glaucoma, highlighting the importance of the route of administration.

**Correct Answer:** Correct Answer: D. Timolol.