At the opening of the nineteenth-century, farmers in America（）

单项选择题The passage is mainly about（）

A．the agriculture revolution
B．the invention of labor-saving machinery
C．the development of scientific agriculture
D．the farming machinery in America

单项选择题Which of the following statements is NOT true（）

A．The need for labor helped the invention of machinery in America
B．The farmer rejected Charles New bolt's plow for fear of ruin of their fields
C．Both Europe and America had great need for farmer machinery
D．It was in Indiana that the first chilled-steel plow was produced