Here's why:
* Linking verbs connect the subject of a sentence to a noun, pronoun, or adjective that renames or describes the subject.
* In the phrase "did have," "did" functions as a helping verb for "have," which in this case is the main verb. However, "have" is not acting as an action verb here. It is being used to link the subject to a noun or pronoun (which is missing in this phrase).
Example:
* "They did have a car." In this sentence, "did have" links the subject "they" to the noun "car."
Let me know if you'd like more examples!