哪些矿石不含结晶水（）。
A、赤铁矿
B、磁铁矿
C、褐铁矿
D、菱铁矿
参考答案：A, B, D
滴眼液的制备
滴眼液的pH为（）
A.5.0～9.0
B.3.5～10.0
C.2.0～8.0
D.5.0～10.0
E.4.0～9.0
In just three years, the Net has gone from a playground for the local people to a vast communications and trading center where millions swap information or do deals around the world.
A．business
B．shopping
C．chatting
D．meeting
