She has a large English vocabulary at her command. 她能灵活运用掌握的大量英语辞汇。
The sense of this word is hard to come at. 这个词的意思不容易掌握。
Here Mr. Casey had placed at my disposal the agreeable villa he was using. 这里，凯西先生把他自己居住的那座舒适的别墅供我自由使用。
Users can make their public keys freely available or place them at a key distribution centre for others to access. 用户可以让公开密钥自由使用或者把公开密钥放在可由别人存取的密钥分配中心。
