在职攻硕英语考试

【单选题】 It can be inferred from the passage that by 1870 ______.
A．the steam engine had been invented
B．a national commission on agriculture had been established
C．the U.S. horse population was about 10 million
D．technology began to be more economical

网考网参考答案：A
网考网解析：
[注释] 根据第二段开始部分，1870年时马和骡子为美国农场的主要劳动力，尽管那时已出现蒸汽机。其他选项的信息有误或没有在短文中涉及。 查看试题解析出处>>