Fill in the gap with the correct present form of the verb in brackets: 1. We ....... (write) this report for four hours. I'm tired. Let's have a break.

The correct answer is A: have been writing.

Explanation:

The sentence indicates an action that started in the past and is still continuing up to the present. Therefore, the present perfect continuous tense (have/has been + verb-ing) is the most appropriate choice.