一个GRE机经填空 快考试了救救孩子！谢谢

南下98UID：3960880

The (i)______ current-generation solar cells are (ii)______: although experimental cells have
reached efficiencies greater than 40 percent, most commercially available cells in the early part of the twenty-first century still struggle to get past about 20 percent.

A. attractions of D. clear
B. limitations of E. unmatched
C. improvements in F. misunderstood

答案是BD 请问CF为什么不可以呀？我的理解是冒号前面的内容和struggle对应，我觉得BD和CF都可以呀~谢谢！

JneasyUID：3870329

冒号后面句子里面没有体现出experimental cell 相比于 commercial cell的提升呀， struggle to get past about 20 percent 和 limitation 更加匹配吧，个人理解哈

南下98UID：3960880

Jneasy 发表于 2019-9-3 13:39
冒号后面句子里面没有体现出experimental cell 相比于 commercial cell的提升呀， struggle to get past ab ...

谢谢！