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 l.5 million barrels by the beginning of next year, but only if non- OPEC nations, including Norway, Mexico, and Russia, were to trim output by a to al 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
题目分析：这几个选项中only if后面有的说output有的没有，后面说的是include一些国家，当然不加output，B和C干掉。D中which指前面的nations，后面用includes主谓不一致，干掉。A和E进行比较，一个加but一个不加，only if的存在已经表明了前后的逻辑关系，不用加but了，并且后面的were to trim和前面的will pare也很难形成对应，杀A。
