The correct option is B) “She had rested on the rock”. Helping verbs are verbs that help the main verb with its meaning and they also set the time of the verb. In this case, the helping verb “had” is helping the main verb “rested”. The auxiliary verb “had” is also setting the verb tense of the sentence, which is past perfect.
The other examples “paddled”, “went” and “swam” are action verbs that do not need a helping verb to extend or add meaning.
