**Core Concept:**
The question is about the reversal of effects of d-tubocurarine, a muscle relaxant that belongs to the class of drugs known as curare derivatives. These drugs work by blocking the acetylcholine receptors in the neuromuscular junction, leading to muscle paralysis and immobility.

**Why the Correct Answer is Right:**
d-Tubocurarine reverses its effects by administering a drug like neostigmine or edrophonium. These drugs belong to a class of medications called cholinesterase inhibitors. Their mechanism of action is to inhibit the enzyme acetylcholinesterase, which is responsible for breaking down acetylcholine. As a result, there is an increased concentration of acetylcholine at the neuromuscular junction, thereby antagonizing the effects of d-tubocurarine and allowing the neuromuscular junction to recover its normal function.

**Why Each Wrong Option is Incorrect:**
A. Atropine: This is a parasympatholytic drug, which blocks the effects of acetylcholine at the muscarinic receptors. It will not antagonize d-tubocurarine's effect.

B. Sugammadex: This is a specific monoclonal antibody that binds to rocuronium and vecuronium, two other neuromuscular blocking agents but not d-tubocurarine.

C. Neostigmine: As explained above, neostigmine reverses the effects of d-tubocurarine by inhibiting acetylcholinesterase, allowing acetylcholine to overcome the blockade and restore normal neuromuscular function.

D. Magnesium sulfate: This drug is a calcium channel blocker, which can suppress tetanic contractions and prevent neuromuscular transmission. However, it does not reverse the effects of d-tubocurarine.

**Clinical Pearl:**
When faced with a patient under d-tubocurarine blockade, choose the correct reversal agent based on the type of neuromuscular blocking agent used. For d-tubocurarine reversal, use neostigmine, not atropine, magnesium sulfate, or sugammadex.