手语交流的局限性有（）
A、看不清
B、推广普及不够
C、地方手语太多
D、手势繁杂
参考答案：B
—_____ that he managed to get the information?
—Oh, a friend of his helped him. [ ]
A. Where was it
B. What was it
C. How was it
D. Why was it
关于氧气的性质叙述正确的是（______ ）
A、在任何条件下，氧气是无色无味的气体 B、氧气的密度比空气小
C、液氧是淡蓝色的液体 D、______．
