Norik had been very happy because he had received two A's
While Vasya was looking for the keys, Petia was sleeping
By the time mom came home, the children were already asleep
Petia was tired, he had been doing English homework for two hours
We had been driving for two hours before reaching the school

Подсказки: Norik (pc), had been (pp), very (pc), happy (pc), because (pc), he (pc), received (pp), two (pc), A's (pc), While (pc), Vasya (pc), was (pc), looking (pc), for (pc), the (pc), keys (pc), Petia (pc), sleeping (pc), By (pc), time (pc), mom (pc), came (pc), home (pc), children (pc), already (pc), asleep (pp), tired (pc), doing (pc), English (pc), homework (pc), two (pc), hours (pc), We (pc), driving (pc), for (pc), before (pc), reaching (pc), school (pc)