Ответ: 1) He looked at the man and understood he (had seen) him somewhere before.2) The secretary asked who (had broken) her typewriter.3) Look! Somebody (has broken) my typewriter.4) They (had bought) the pears in the market.5) The children said they (had walked) 5 miles.6) We wondered what they (had been doing) since we last met.7) My friends are hungry because they ( have had) nothing to eat since morning.8) We have just (been walking) in the park.9) When my parents came home they saw that someone (had eaten) the dinner.10) Peter hoped there (had been) no bad news since Sunday.