**Core Concept**
The facial nerve, also known as the seventh cranial nerve, has several branches that innervate muscles of facial expression and provide sensory innervation to the ear. As it traverses the temporal bone, it passes through the facial canal, where it gives off several branches.

**Why the Correct Answer is Right**
The facial nerve has three branches within the facial canal: the greater petrosal nerve, the nerve to the stapedius, and the chorda tympani. The greater petrosal nerve arises from the geniculate ganglion and provides parasympathetic innervation to the lacrimal gland and mucous membranes of the nasal cavity. The nerve to the stapedius arises from the facial nerve in the facial canal and innervates the stapedius muscle, which stabilizes the stapes bone in the middle ear. The chorda tympani arises from the facial nerve in the facial canal and carries taste fibers from the anterior two-thirds of the tongue and also provides parasympathetic innervation to the submandibular and sublingual glands.

**Why Each Wrong Option is Incorrect**
**Option A:** The greater petrosal nerve is a branch of the facial nerve, but it is not the only branch within the facial canal.

**Option B:** The nerve to the stapedius is a branch of the facial nerve, but it is not the only branch within the facial canal.

**Option C:** The chorda tympani is a branch of the facial nerve, but it is not the only branch within the facial canal.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the facial nerve has three branches within the facial canal: the greater petrosal nerve, the nerve to the stapedius, and the chorda tympani. This knowledge is crucial for understanding the anatomy of the facial nerve and its functions.

**✓ Correct Answer: D. All**