He tried his best to solve the problem, ________ difficult it was.
---Go and get Lily to write for the wall newspaper. ----Why _______?couldn’t I do better?
It is thought that one billion people I the world, ______is half the word’s workers, earn their living by farming.
—Hold the ladder for me! —That’s______
I think I was at school,______I was staying with a friend during the vacation when I heard the news.
There were two boys in the lab,______did the experiment successfully.