15) The boy __________ (notice) that a girl __________ (watch) him. 16) My granddad __________ (fall) off the ladder while he __________ (paint) the ceiling. 17) While they __________ (wait), they __________ (surf) the Net. 18) Tim __________ (become) sick while he __________ (travel) in China. 19) What __________ (you, do) when you __________ (hear) about the accident? 20) My sister said that she __________ (not feel) happy, so I __________ (talk) to her.

Решение:

1. The boy noticed that a girl was watching him.
2. My granddad fell off the ladder while he was painting the ceiling.
3. While they were waiting, they were surfing the Net.
4. Tim became sick while he was travelling in China.
5. What were you doing when you heard about the accident?
6. My sister said that she was not feeling happy, so I talked to her.

Ответ: noticed, was watching; fell, was painting; were waiting, were surfing; became, was travelling; were you doing, heard; was not feeling, talked.