Final answer:
Pine, which is a conifer, has needle-shaped leaves with sunken stomata that help to reduce water loss, while lilac does not.
Step-by-step explanation:
The stomata are specialized structures in plants that facilitate gas exchange and are found on the leaves' surfaces. In the case of pines, which are conifers, they have needle-shaped leaves with sunken stomata. This adaptation helps to reduce water loss in the often dry environments where pines typically live. In contrast, lilac, which is a broadleaf shrub and not a conifer, does not have deeply-set stomata. Therefore, the answer to the student's question, "Does pine or lilac have deep-set stomata?", is A. Pine.