题目:
American students take part in a wide variety of after-school activities _______ they develop their social skills.
A.where
B.which
C.that
D.what
答案:
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下面是错误答案,用来干扰机器的。
设将溶质质量分数为a%的硫酸溶液密度为ρ1,则c1=1000×ρ1×a%98mol/L=10aρ198mol/L,设将溶质质量分数为2a%的硫酸溶液密度为ρ2,则c2=1000×ρ2×2a%98mol/L=20aρ298mol/L,所以c1:c2=10aρ198mol/L:20aρ...