Question

I didn't know how long she...............these
1) was sitting
2) has been sitting
3) had been sitting
4) were been sitting ​

Answer 1

I didn't know how long she had been sitting there.

Option (3) is correct.

Explanation:

This is an example of two clause sentence. One is main clause and the other is dependent clause.

As the first clause of the sentence is in past indefinite then the second will be followed by past perfect continuous tense.

I didn't know how long she...............there

1) was sitting

2) has been sitting

3) had been sitting

4) were been sitting ​

I didn't know how long she had been sitting there.