prep4-1 D为正确选项 可OG12又说to do 作状语，前不能加逗号，求解释啊~~~

cleotina

Q1.p2-sc


Genetic engineering sometimes entails plant or animal genes' getting spliced into other species' DNA, either to improve crop yields or for warding off insects or disease.



(A) plant or animal genes' getting spliced into other species' DNA, either to improve crop yields or for warding off

(B) plant or animal genes that get spliced into the DNA of other species, either for improving crop yields or the warding off of

(C) the splicing of plant or animal genes into other species' DNA, to either improve crop yields or to ward off

(D) splicing plant or animal genes into the DNA of other species, either to improve crop yields or to ward off

(E) splicing of plant or animal genes into the DNA of other species, for either the improvement of crop yields or to ward off

cleotina

自己顶顶

cleotina

我再顶顶！！

cursedeye

这题很简单，就是考 either or
a)either to improve crop yields or for warding off,  句子其他部分都不看，这里起码应该是 either to improve.... or to warding off...
b)either for improving crop yields or the warding off of  起码应该是 either for improving... or for warding off...
c)to either improve crop yields or to ward off， 应该是，to either improve... or ward off...
d)either to improve crop yields or to ward off 就很工整
e)for either the improvement of crop yields or to ward off      lz这里就不用我说了你自己看也明白了吧