检查阿司匹林中的水杨酸杂质可用（）
A、与变色酸共热呈色
B、与HNO3显色
C、与硅钨酸形成白色↓
D、重氮化偶合反应
E、以上都不对
参考答案：E
The police were trying to _____ where the drug dealers were _____ it suddenly dawned upon them
that they might be hidden somewhere 10 miles within the border between the two countries. [ ]
A. come out; when
B. make out; while
C. figure out; when
D. think out; since
目前我国的天然气净化工艺较国外水平（）。
A、先进
B、远远落后
C、基本赶上
D、无法比较
