—Who has made a mess in my room?—Who else it but your naughty son?
---I went to the History Museum last summer. ----Did you go ___?
He is ill, and he has ___ in bed for a week.
We’ve made up our mind to finish this experiment no matter ___ difficult it was.
His doctor suggested he ___ smoke because of his illness.
---It’s a wonderful party.—It’s very nice of you to come.___.