What is the linking verb in sentence suddenly it turned very dark and wind began to blow fiercely?

The linking verb in the sentence "Suddenly it turned very dark and wind began to blow fiercely" is turned.

Here's why:

* Linking verbs connect the subject of a sentence to a word or phrase that describes or renames the subject.

* In this sentence, "it" is the subject, and "very dark" describes the state of "it".

* The verb "turned" links the subject "it" to the description "very dark".

The other verb in the sentence, "began", is an action verb. It describes the action of the wind.