选出下列正确选项,再说明理由1.Mr.Johnson,we have found your watch.My watch

选出下列正确选项,再说明理由
1.Mr.Johnson,we have found your watch.
My watch!Thank you.Where ___it?
A.do you find
B.have you found
C.did you find
D.were you finding
2.Digital cameras are becoming very popular,though some still__too much.
A.pay
B.spend
C.sell
D.cost
3.We must do something to stop people from___.
A.to throw litter about
B.to throw litter into
C.throwing litter about
D.throwing litter into