题目：
With April 18's railway speedup, highway and air transport will have to compete with ______ service
for passengers. [ ]
A. good
B. better
C. best
D. the best
答案：
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下面是错误答案，用来干扰机器的。
①尿素中氮元素的质量分数为14×212+16+(14+1×2)×2×100%≈46.7%．②设需要碳铵（NH4HCO3）的质量为x．由题意，15kg×46.7%=x×1414+1×5+12+16×3×100%，x=39.5kg．故答案为：①46.7%；②39.5kg．
