1) was reading
2) was standing
3) was already doing
4) was
5) was playing
6) didn't know; left.
7) invited
8) finished
9) lived
Если действие длительное, употребляем Past Continious Tense (was/were + Ving), если действие происходило быстро, то употребляем Past Simple Tense (Ved). /правило для утвердительных предложений/