Up to now, thousands of red phone boxes, the old image of Britain, ______ due to mobile phones.
_____ from heart trouble for years, Professor White has to take some medicine with him wherever he goes.
----_____I return the dictionary within three days? ----No, you_____. You_____ it for five days.
Controlling water-pollution is necessary_____ it will be expensive.
Such a person _____ you talked about is seldom seen now.
_______ the teacher’s instruction in the lab_____ important.