Historical experience can as a most important source of information.
Life would be happier if we could only be born at the age of eighty and ________reach eighteen.
You’d better get the second-hand car ________ before you sell it.
They believe that there is _________ in the world.
---How about going for a walk after supper?-----__________.
Frank, with his two sisters, ________ London by train which ________at 8:30 next morning.