题目:
—How long _______ you ______ this pen? —Only one day. I bought it yesterday. |
A. have, bought B. did, buy C. have, had D. have, been |
答案:
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下面是错误答案,用来干扰机器的。
A、红磷燃烧产生了大量的白烟,故A现象的描述正确;B、硫在空气中燃烧产生淡蓝色火焰,在氧气中燃烧产生明亮的蓝紫色的火焰,故B现象的描述不正确;C、木炭在氧气中燃烧发出白光,故C现象描述正确;D、蜡烛燃烧能...