A. 1) They had eaten...

2) Had you finished the report...

3) Jennifer had bought the house...

4) What had she done that...

5) Our boss hadn't made the decision...

6) The students had written the report...

7) Mark had wanted to go...

B. 1) had left / arrived

2) started / had finished

3) had seen / came

4) hadn't spoken / moved

5) had got / reached

C. 1) I didn't tell the teacher that my mum had helped me with my homework

2) Paul didn't say that he had taken Albert's watch

3) The bike was much more expensive than he had thought first

4) Dad drove me home after I had fallen into the water

5) Marion asked me what had happened to me last week

6) We had eaten two Big Macs before we went home