属于乙类传染病的是( )
A．鼠疫B．流行性感冒C．艾滋病D．麻风病E．流行性腮腺炎
参考答案：C
The computer system ______ suddenly while he was searching for information on the Internet. [ ]
A. broke down
B. broke out
C. broke up
D. broke in
欲鉴别氢气、氧气、二氧化碳、甲烷4种气体，现有一盒火柴，还需要用到下列实验用品中的[ ]
A．装有蒸馏水的烧杯
B．装有无色酚酞的烧杯
C．冷而干燥的烧杯
D．内壁蘸有澄清石灰水的烧杯
