Which of these sentences below uses the word turned as a linking verb.

A. The milk turned sour after sitting out on the counter all night.

B. She turned the doorknob but the door was locked.

C. Have you turned in you writing assignment yet?

The correct answer is: A. The milk turned sour after sitting out on the counter all night.

There are verbs in the English language followed either by an adjective or a noun, and we call them linking verbs. Some of these verbs are: be, appear, look, remain, seem, and turn, like in the example above.

Linking verbs are verbs which link the subject with more information about it, or connect the subject with the sentence cemplement.

The correct option is A) "The milk turned sour after sitting out on the counter all night."

The linking verb "turn" in this case is linking the subject "the milk" with its subject complement "sour". The purpose of linking verbs is to add more information to the subject and to show a link between subject and subject complement.

Options B and C and incorrect as the verb "turn" is used as an action verb in both cases.