Final answer:
The helping verbs in the sentences are 'is', 'has', and 'will'.
Step-by-step explanation:
The helping verbs in the given sentences are:
- is - He is writing a report.
- has - He has read the book.
- will - She will study for the test.
Helping verbs are used with main verbs to express tense, voice, and mood. In these sentences, the helping verbs indicate present tense for the first sentence, past tense for the second sentence, and future tense for the third sentence.
Learn more about Helping verbs