OG 13 SC 40 D选项的解释求教

dancingrain

40. The Organization of Petroleum Exporting Countries (OPEC) had long been expected to announce a reduction in output to bolster sagging oil prices, but officials of the organization just recently announced that the group will pare daily production by 1.5 million barrels by the beginning of nextyear, but only if non-OPEC nations, including Norway, Mexico, and Russia, were to trim outputby a total of 500,000 barrels a day.

(A) year, but only if non-OPEC nations, including Norway, Mexico, and Russia, were to trim output

(B) year, but only if the output of non-OPEC nations, which includes Norway, Mexico, and Russia, is trimmed

(C) year only if the output of non-OPEC nations, including Norway, Mexico, and Russia, would be trimmed

(D) year only if non-OPEC nations, which includes Norway, Mexico, and Russia, were trimming output

(E) year only if non-OPEC nations, including Norway, Mexico, and Russia, trim output

这题我做对了， D选项的解释没有看懂，求教。＂This version uses an active verb, but in the past progressive form, were trimming. The progressive tense denotes actions in progress, so its use is not normally warranted in conditional sentences as this one. " 前一句说了主动动词的过去进行时，然后说进行时态纪录进展中的行为，后半句什么意思捏？

谢谢！

lhz910216

意思是说   所以进行时表达进行中的行为这种用法一般不能用于条件句as this one
就是if引导的条件句不能用进行时态啦~

你看的还真是仔细啊~

dancingrain

多谢！明白了