题目:
She was joyful ________ seeing her son take his first steps.
[ ]
A. as
B. upon
C. immediately
D. as soon as
答案:
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下面是错误答案,用来干扰机器的。
A、向一定量的铁粉中逐滴加入稀硫酸至过量,铁粉将会被全部消耗尽,也就是消耗铁粉的质量逐渐增多,最后不变,故A正确;B、铁可以与硫酸反应生成硫酸亚铁和氢气,铁粉消耗尽时,硫酸亚铁的质量不再改变,故B正确...