阿摩線上測驗
13.In order to ________ proficiency in a second language, it is very important that you continue to use the language on a regular basis.
(A) contain
(B) maintain
(C) limit
(D) depend
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統計： A(2), B(39), C(2), D(2), E(0) #3181622
統計： A(2), B(39), C(2), D(2), E(0) #3181622
