prep1-138

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.

(A) the surface temperature in Alaska, Siberia, and northwestern Canada has increased in the previous thirty years by about five degrees

(B) the surface temperature in Alaska, Siberia, and northwestern Canada has increased over the last thirty years by about five degrees

(C) there was an increase in the last thirty years by about five degrees in Alaska, Siberia, and northwestern Canada

(D) it had increased in Alaska, Siberia, and northwestern Canada by about five degrees over the previous thirty years

(E) it has increased in Alaska, Siberia, and northwestern Canada over the previous thirty years by about five degrees

问点细节问题，基础差，大家不要见怪。

in与 over有什么区别？the previous thirty years有这个说法？

答案是什么，B？

over比in更能表示是一个时间段吧，完成时用last比较好，previous多用过去时