9. Because of increases in the price of oil and because of government policies promoting energy conservation, the use of oil to heat homes fell by 40 percent from 1970 to the present, and many homeowners switched to natural gas for heating. Because of switching to natural gas involved investing in equipment, a significant switch back to oil in the near future is unlikely.
the prediction that ends the passage would be most seriously called into question if it were true that in the last few years
A. the price of natural gas to heat homes has remained constant, while the cost of equipment to heat homes with natural gas has fallen sharply.
B. the price of home heating oil has remained constant, while the cost of equipment to heat homes with natural gas has risen sharply.
C. the cost of equipment to heat homes with natural gas has fallen sharply, while the price of home heating oil has fallen to 1970 levels.
D. the cost of equipment to heat homes with oil has fallen sharply, while the price of heating with oil has fallen below the price of heating with natural gas.
E. the use of oil to heat homes has continued to decline, while the price of heating oil has fallen to 1970 level.
谁能帮我分析一下这道题目文章的逻辑
然后选项部分，我虽然选了D，但我在B、D之间犹豫过，所以想请教D具体为什么是对的？作者: lihaolan 时间: 2013-4-10 17:42
削弱题。题目说油价上涨，导致换装置用天然气。因为换回用油要重新购置装置，所以换回油不可能。
B说油价不变，换天然气装置价格变高。其实跟文章的premise 和conclusion无关。题目是说因为换回用油要重新购买装置，所以不可能重新使用油。和天然气装置无关。因为已经换成了天然气了。
D油的装置便宜了，油价下降了。因此削弱了premise 和conclusion的练习。即使要换装置也有是可以接受的。作者: yangrryq 时间: 2013-4-10 22:06
B. the price of home heating oil has remained constant, while the cost of equipment to heat homes with natural gas has risen sharply. 用天然气的人们早就买好了机器，如果涨价也没有大的影响。石油价格已经很高了，保持不变不能质疑文章的观点。
D. the cost of equipment to heat homes with oil has fallen sharply, while the price of heating with oil has fallen below the price of heating with natural gas.
切中要害。用石油的机器价格无限接近于0，随便买，然后用石油价格比天然气还低，当然可以考虑换回用石油。作者: briefcandle 时间: 2013-4-13 07:47
oil 和natural gas 的比较，比较的是两个factor: equipment cost and price of heating
而结论说switch to oil is unlikely的原因不只是因为现阶段price of heating with oil贵，而且很多人已经买了natural gas的equipment