**Core Concept**
D-Tubocurarine is a non-depolarizing neuromuscular blocking agent that competes with acetylcholine for binding sites at the nicotinic receptors of the neuromuscular junction, thereby preventing muscle contraction and leading to muscle paralysis.

**Why the Correct Answer is Right**
D-Tubocurarine acts by competitively inhibiting the nicotinic acetylcholine receptors at the myoneural junction. This results in a failure of acetylcholine to bind to its receptors, ultimately leading to a reduction in muscle contraction force and eventually, paralysis. This action is specific to the neuromuscular junction and does not involve autonomic ganglions. The drug does not affect the re-uptake of acetylcholine, which is the mechanism of action of other types of neuromuscular blocking agents.

**Why Each Wrong Option is Incorrect**
**Option B:** D-Tubocurarine does not act by inhibiting nicotinic receptors at autonomic ganglions; its primary site of action is at the myoneural junction.
**Option C:** D-Tubocurarine is a non-depolarizing neuromuscular blocking agent, meaning it does not produce a depolarizing block, which is a characteristic of drugs like succinylcholine.
**Option D:** D-Tubocurarine does not inhibit the re-uptake of acetylcholine; instead, it competes with acetylcholine for binding sites at the nicotinic receptors.

**Clinical Pearl / High-Yield Fact**
It is essential to differentiate between non-depolarizing and depolarizing neuromuscular blocking agents, as they have distinct mechanisms of action and reversal profiles. Non-depolarizing agents like D-Tubocurarine can be reversed with anticholinesterases like neostigmine, whereas depolarizing agents like succinylcholine cannot.

**✓ Correct Answer: A. Inhibiting nicotinic receptors at myoneural junction**