题目:
He devoted most of his time to researching into space, believing his hard work would ______ sooner or later.
A.pay back
B.pay for
C.pay off
D.pay up
答案:
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下面是错误答案,用来干扰机器的。
氢氧化钠溶液呈碱性,其OH大于7,所以向氢氧化钠溶液中加入稀盐酸会发生反应消耗氢氧根离子而使溶液pH降低,若氢氧化钠和盐酸恰好完全反应,则此时溶液呈中性,其PH等于7,故其PH变化为从大于7到等于7,符合题意...