21．All the Chinese are looking forward to our country’s first _________ to land on the moon after the successful trip of Chang’e to it．

A．practiceB．purpose  C．attemptD．act

22．My father never ______ the idea that money brings happiness．

A．relates to B．subscribes to

C．caters to  D．contributes to

23．—Where does Jack work?

—I’m not sure, but he worked at Motorola when I last met him, _________．

A．however B．though C．yet D．anyhow