The agricultural revolution in the 19th century involved two things ：the invention of labor-saving machinery and the deyelopment of scientific agriculture.Labor-saving machinery naturally appeared first where labor was scarce. “In Europe ，”said Thomas Jefferson ，“the object is to make the most of their land ，labor being abundant：here it is to make the most of our labor ，land being abundant. ”It was in America ， therefore，that the great advances in 19th century agricultural machinery first came. At the opening of the century ，with the exception of a crude plow farmers could have carried pracically all of the existing agricultural implements on their backs ;by1860，most of the machinery inuse today had been designed in an early form.The most important of the early inventions was the iron plow.As early as 1790 Charles Newbold of New Jersey had been working on the idea of a cast-iron plow and spent his entire fortune in introdueing his invention.The farmers，however，would have none of it ，claiming that the iron poisoned the soil and made the weeds grow.Nevertheless，many people devoted their attention to the plow ，until in 1869 James Oliver of South Bend ，Indiana，turned out the first chilled-still plow. ? 1. What is the main topic of the passage ? a.The need for agricultural advances to help feed a growing population. b.The development of safer machines demanded by the labor movement. c.Machinery that contributed to the agricultural revolution. d.New Jersey as a leader in the agricultural revolution. 2. The expression “make the most of ” in Line 4is closest in meaning to which of the following ? a.get the best yield from  b.raise the price of  c.make full use of  d.earn a living on 3. Which of the following can be inferred from what Thomas Jefferson said ? a.Europe was changing more quickly than America. b.Europe had greater need of farm machinery than America did. c.America was finally rnning out of good farmland. d.There was a shortage of workers on American farm. 4. It can be inferred that the waord “here”in Line 4 refers to_____. a.Europe b.America c.New Jersey d.Indiana 5.What point is the autor making by stating that farmers could carry nearly all their tools on their backs? a.Farmers had few tools before the agricultural revolution b.Americans were traditionally self-reliant. c.Life on the farm was extremely difficult. d.New tools were designed to be portable.