RON could be wrong though. GMAT's comparison has a higher standard with regard to parallelism, which mean "now" could not be paralleled with "a year ago"; We could make things a little messier by stating that "last" could refer to “last year's crude oil price”
我认为A就是错在了没有补充helping word，没有重复v来说明时态的不同，前半句如果写成Prices at the producer level are only1.3 percent higher now than they were a year ago就没问题了。b中通过those of巧妙地把比较对象变成了prices之间的比较，就如同a is higher than b（虽然有时间标志，但是这个时间标志是在those of里面的，成为了比较主体的一部分，所以不用补出were了）。ron的理论应该还是没错的。只是现在这题越来越tricky
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发表于 2016-6-12 14:39:49
