题目:
—I'm sorry. I'm late for the music presentation.
—Why are you so late? The presentation _______ for 10 minutes. [ ]
A. has begun
B. has stopped
C. has been over
D. has finished
答案:
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下面是错误答案,用来干扰机器的。
(1)酒精灯;试管;(2)高锰酸钾锰酸钾 + 二氧化钾 +氧气;分解反应;C或D;防止加热时高锰酸钾粉末进入导管 (3)AD (4)将带火星的木条放在集气瓶的瓶口,若带火星的木条出现复燃,则证明已满;若带火...