Oh, you have a headache and a cough. __________ have you been like this? —Two days.[ ]
Some scientists think that it may take ______ years to make robots look like people, and do the same things as us.
Why are you so tired these days?—Well, I have ________ homework to do.
He knows _______ English but he has _____ English friends.
There _____ calories in water.