— Miss Yang doesn’t look well. What’s wrong with her?— Oh, she has some trouble ______ her baby well.

-- Can we make this plan a week later?-- No, we can’t put off _______ it because the meeting is only two days from now.

---How did you work out the difficult chemistry problem?--- I worked it out by ________.

When I was in primary school, I had trouble ______complete sentences.

Simon made a big bamboo box _______ the little sick bird till it could fly.