You never know you need it _______you lose it.

“Never for a second，”the boy says，“________that my father would come to my rescue.” (2013·江苏，27)

Is this ________ key, Tom —No, that one is ________.

We arefriendly ______our new classmates.

China is nolonger ___ a production base； it is also one of the most important consumermarkets