Grammar
1.
1. a 2. a 3. b 4. b 5. b
2.
1. have just opened
2. forgot to put the keys back on the table
3. had never been skydiving
4. has been raining since last night
5. had been playing the piano for ten years before giving it up / she gave it up
6. can’t stand seeing him so frustrated
7. stopped to rest because they were tired from walking
8. remember locking the door (when I left the house)
3.
1. appearing 5. has applied
2. had borrowed 6. calling
3. has been building 7. had been climbing
4. to check 8. receiving
4.
1. discovered 6. becoming
2. was standing 7. to contact
3. hesitating 8. hadn’t heard
4. jumped 9. being
5. was approaching 10. sharing
