Question

What is the present perfect progressive tense of the verb ''to investigate''.

Detectives _____ for months.

A.
have been investigating

B.
investigate

C.
were investigating

D.
have investigated

Answer 1

The present perfect progressive tense of "to investigate" is A. have been investigating.

The present perfect progressive tense indicates a continuous action that is either still occurring or was completed in the past.
"has been" + present participle

Hope this helps! :)

Answer 2

A. Have been investigating
Pretty sure that's it.