basedon3Cex.2
Choosethecorrectitem.

1. Howlong[had you been waiting|were you waiting]beforethebusarrived?
2. Pam[went|had gone]outwithherfriendsaftershehadfinishedherhomework.
3. Wecouldn'tleavethelabuntilwe[cleaned|had cleaned]thecultureplatesfirst.
4. IlostmykeysasI[was walking|had been walking]home.