____ is known to us all that the old scientist , for ____ life was hard in the past, still works hard in his eighties.
I ______ for London tonight, for there is ______ an important meeting there.
----I _____this morning, but he could not come. ----Well, we’d better go and _____at his office.
_____ 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.