Here's why:
* Linking verbs connect a subject to a noun or adjective that renames or describes the subject. Common linking verbs include "be" (is, am, are, was, were, been, being), seem, appear, become, feel, look, smell, sound, taste.
* In this sentence, "loves" is an action verb. It describes what David is doing.
Let me know if you'd like to practice with some other sentences!