Question

She is reading an interesting book since

morning.​

Answer 1

She has been reading a interesting book since morning

Answer 2

Explanation:

She has been reading an interesting book since morning .

Here since is the keyword to notify the tense of the sentence .

This is in the form of Present Perfect Continuous formula of this sentence (Sub + have/has + been + past participle (ing form) +object).

Rule : This tense is used to express an action which began at some point of time in the past and is still continuing .