Step 1: Recall the anatomy.
In horses, the cervical vertebrae (C1–C7) lie well below the crest of the neck. They trace a gentle S-curve: relatively low through mid-neck and then turn upward toward the poll.
Step 2: Match each drawing to the anatomy.
(A) and (B) keep the red line too close to the neck’s crest ⇒ anatomically inaccurate.
(D) shows an almost straight, horizontal line ⇒ ignores the natural upward curve near the poll.
(C) places the line low through the neck and curves it upward behind the jaw ⇒ this best matches the real cervical column path.
Step 3: Conclude.
Thus, the most correct schematic is \(\boxed{\text{C}}\).
Final Answer:
\[
\boxed{\text{(C)}}
\]