**Core Concept**
The question is testing the understanding of the trochlear nerve (CN IV) and its relationship with the superior oblique muscle, as well as the oculomotor nerve (CN III) and its relationship with the inferior rectus muscle. This involves the anatomy of the extraocular muscles and their innervation.

**Why the Correct Answer is Right**
The left superior oblique muscle is innervated by the trochlear nerve (CN IV), which is the thinnest and longest cranial nerve. This nerve arises from the dorsal aspect of the midbrain and descends to innervate the superior oblique muscle. In contrast, the left inferior rectus muscle is innervated by the oculomotor nerve (CN III), which arises from the midbrain and descends to innervate several muscles, including the inferior rectus.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the correct nerves innervating the muscles.
* **Option B:** This option is incorrect because it does not accurately describe the relationship between the superior oblique and inferior rectus muscles and their respective nerves.
* **Option C:** This option is incorrect because it is incomplete and does not provide a clear description of the trochlear and oculomotor nerves.
* **Option D:** This option is incorrect because it is not a valid description of the nerves innervating the superior oblique and inferior rectus muscles.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the trochlear nerve (CN IV) is the only cranial nerve that decussates (crosses over) before exiting the brainstem, making it unique among the cranial nerves.

**Correct Answer:** A. Left superior oblique is innervated by the left trochlear nerve (CN IV), and the left inferior rectus is innervated by the left oculomotor nerve (CN III).