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题库 / Prep2007E1-SC-138
According to scientists at the University of Alaska, while the surface temperature of the globe has risen over the last century by about one degree Fahrenheit, the surface temperature in Alaska, Siberia, and northwestern Canada has increased in the previous thirty years by about five degrees.
the surface temperature in Alaska, Siberia, and northwestern Canada has increased in the previous thirty years by about five degrees
the surface temperature in Alaska, Siberia, and northwestern Canada has increased over the last thirty years by about five degrees
there was an increase in the last thirty years by about five degrees in Alaska, Siberia, and northwestern Canada
it had increased in Alaska, Siberia, and northwestern Canada by about five degrees over the previous thirty years
it has increased in Alaska, Siberia, and northwestern Canada over the previous thirty years by about five degrees
简单粗暴的ronTAT
RON：Because the two parts express similar facts, they should be expressed as similarly as possible. (This isn't grammatical parallelism, strictly speaking, but the idea is the same.)
The first part uses "over". So, the second part"”which uses exactly the same sort of time construction"”should use "over", too.
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