----- I try to memorize new words every day, but only remember few of them.

----- That’s not surprising. Newly-learnt words are easily forgotten unless frequently _____ in communication.

A. used          B. using         C. to use         D. be used

一I try to memorize new words every day, but can only remember few of them．

一That’s not surprising．Newly-learnt words are easily forgotten unless frequently _______ in communication．

A．used                       B．using                C．to use                 D．be used