第1个回答 2012-05-13
Students have already mastered certain amount of vocabulary.
一定量的就是certain amount of 啊。。
第2个回答 2012-05-01
The students have grasped certain vocabulary.
一定:must
这个must在这个句子里有点特殊
第3个回答 2012-05-01
The students have mastered enough vocabulary.
第4个回答 2012-05-01
The students have mastered the vocabulary.本回答被提问者采纳
第5个回答 2012-05-01
The students have acquired a somewhat large vocabulary