Past Perfect vs Past Perfect Continuous

It was a relief to find the documents. I (look) (a)   for them all afternoon.

He was dismissed, even though, in his opinion, he (not/do) (a)   anything wrong

The passengers were cross because the airline (a)   (lose) everyone's bags.

I was delighted when I found my keys. I (a)   (look) for them for hours

He called me at eleven in the evening to tell me that he (find/finally) (a)   a solution.

We (work/already) (a)   on this project for a month before we found a fundamental flaw.

By the time I came back from my business trip, a lot of things (a)   (changed) .

The doctor asked me how long I (have) (a)   the symptoms.

The children were wet because they(play) (a)   football in the rain.

I (not / see) (a)   Jacob for several years, but I recognised him immediately.