再问两道xdf的烂题~~~

126. The level of lead contamination in United States rivers declined between 1975 and 1985. Federal regulations requiring a drop in industrial discharges of lead went into effect in 1975, but the major cause of the decline was a 75 percent drop in the use of leaded gasoline between 1975 and 1985.

Which of the following, if true, best supports the claim that the major cause of the decline in the level of lead contamination in United States rivers was the decline in the use of leaded gasoline?

B. Most of the decline in industrial discharges of lead occurred before 1976, but the largest decline in the level of river contamination occurred between 1980 and 1985.

不太明白正确选项的意思, 为什么把时间分成这样子?

130. It is widely assumed that a museum is helped financially when a generous patron donates a potential exhibit. In truth, however, donated objects require storage space, which is not free, and routine conservation, which is rather expensive. Therefore, such gifts exacerbate rather than lighten the demands made on a museum's financial resources.

Which of the following, if true, most seriously weakens the argument above?

E. Objects donated by a patron to a museum are often of such importance that the museum would be obliged to add them to its collection through purchase if necessary.

不明白怎么就削弱结论了? through purchase不就是加剧了museum's financial resources吗?

B.说明由于discharge of lead造成的效果在1976年前就发生了，而最大的decline发生在1980-1985很显然是由于别的原因，也就支持了gasoline是原因的结论

E: 说捐的展品实际加剧了博物馆的经济负担

但是如果没有人捐，博物馆就不得不需要去买的的话，捐的展品实际上是减轻了负担