一道逻辑题，感觉跟不等式一样

王Alcal1011

12. Photovoltaic power plants produce electricity from sunlight. As a result of astonishing recent technological advances, the cost of producing electric power at photovoltaic power plants, allowing for both construction and operating costs, is one-tenth of what it was 20 years ago, whereas the corresponding cost for traditional plants, which burn fossil fuels, has increased. Thus, photovoltaic power plants offer a less expensive approach to meeting demand for electricity than do traditional power plants.

The conclusion of the argument is properly drawn if which one of the following is assumed?

(A) The cost of producing electric power at traditional plants has increased over the past 20 years.

(B) Twenty years ago, traditional power plants were producing 10 times more electric power than were photovoltaic plants.

(C) None of the recent technological advances in producing electric power at photovoltaic plants can be applied to producing power at traditional plants.

(D) Twenty years ago, the cost of producing electric power at photovoltaic plants was less than 20 times the cost of producing power at traditional plants.

(E) The cost of producing electric power at photovoltaic plants is expected to decrease further, while the cost of producing power at traditional plants is not expected to decrease.

答案是D.
一直没想通，觉得再怎么想，那个20倍都不严密。

berries

它说whereas the corresponding cost for traditional plants, which burn fossil fuels, has increased，这里用的是increase，言下之意是增长幅度最多也没有到翻倍的地步（根据常识判断也没有增长那么多）

已知0.1 X 20年前photovotaic的cost<20年前Traditional的cost+increase
=>20年前photovotaic的cost<10 X (20年前Traditional的cost+increase)

如果20年前photovotaic的cost<20 X 20年前Traditional的cost
只有当increase>=20年前Traditional的cost时，已知才不成立

所以这样子推断还是比较严密的

khalo

注意省题
if assumed =/= must assume

jimli

把题抄错了。

D选项里是“less than 10 times”。