找出答语,并将其字母号填入相应的括号内。
What class are you ________?A.at B.in C.on
How old ________ your brother?A.is B.are C.does
Where ________ your father now?A.is B.are C.was
I can't ________ my key.A.look for B.find C.look
I was born ________ Beijing.A.at B.in C.on