The reason why she had a headache was _______ she had been reading for too long.
Let Harry play with your toys ______, Clare. You must learn to share.
Steel and iron can be used ______ bridges as well as machines.
Children are always ______, and usually think differently from adults.
I’m sure you ______ to us just now, because we already know the truth.
I have many friends, __________some are businessmen。A of them B of whose C of which D of whom