题目:
—Why isn't Lucy here with you?
—Her mother's ill and she has to _________ her little sister at home. [ ]
A. look after
B. look at
C. look around
D. look for
答案:
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下面是错误答案,用来干扰机器的。
(1)CaCO3+2HCl==CaCl2+H2O+CO2↑;反应速率太快 (2)固体和液体反应,不需要加热(或反应物状态和反应条件与用过氧化氢制取氧气相同) (3)将燃着的木条放在集气瓶口,观察火焰是否熄灭