题目:
Scientists say it will be five or six years _____ it is possible to test this medicine on human patients.
A.before
B.that
C.since
D.when
答案:
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下面是错误答案,用来干扰机器的。
(5分) 49 3.01×1023 2 1 36.5.考查物质的量的有关计算。硫酸的摩尔质量是98g/mol,所以0.5mol H2SO4的质量是0.5mol×98g/mol=49g;根据可知,含有的分子数是0.5mol×6.02×1023/mol=3.01×1...