30. Choose the correct option to complete each sentence.
1. Rich countries __ more to help poorer ones in my opinion.
a shall be doing b can be doing c should be doing

2. He __ earlier on if he doesn’t know what to do now.
a can’t be listening b can’t have been listening c can’t listen

3. I suppose she __ it back at the office. It’s definitely not here.
a might leave b might have left c might be leaving

4. I __ that it’s not as easy as I thought.
a can see b would see c must see

5. There’s only one answer. It __ by the builders when they finished.
a must have been taken b must be taking c must have been taking