一道cr2 的逻辑题 求高手解答！！

scholar

82.  (33511-!-item-!-188;#058&007598)   答案选  c
Technologicalimprovements and reduced equipment costs have made converting solar energydirectly into electricity far more cost-efficient in the last decade.  However, the threshold of economic viabilityfor solar power (that is, the price per barrel to which oil would have to risein order for new solar power plants to be more economical than new oil-firedpower plants) is unchanged at thirty-five dollars.
Whichof the following, if true, does most to help explain why the increasedcost-efficiency of solar power has not decreased its threshold of economicviability?
A.The cost of oil has fallen dramatically.
B.The reduction in the cost of solar-power equipment has occurred despiteincreased raw material costs for that equipment.
C.Technological changes have increased the efficiency of oil-fired power plants.
D.Most electricity is generated by coal-fired or nuclear, rather than oil-fired,power plants.
E.When the price of oil increases, reserves of oil not previously worthexploiting become economically viable.

sdcar2010

This is a paradox question, for which you need to provide a clause to explain the discrepancy.  C does that.

If both the oil-fired and solar-powered plants increase their efficiency, the threshold of economic viability for solar power remains unchanged.

scholar

还不是很明白 这里的门槛到底是一种什么关系？

sdcar2010

The meaning of "the threshold of economic viabilityfor solar power " is defined as "price per barrel to which oil would have to risein order for new solar power plants to be more economical than new oil-firedpower plants."

In other words, the price of oil at which the power generated by the solar power plant is cheaper that by oil-fired power plants.