求教GWD2-Q31

masushuang

In the mid-1970’s, since birds were overcome by pollution, and routinely falling from the sky above Los Angeles freeways, this prompted officials in California to devise a plan that reduced automobile emissions.

A. since birds were overcome by pollution, and routinely falling from the sky above Los Angeles freeways, this prompted officials in California to devise a plan that reduced
B. since birds that had been overcome by pollution were routinely falling from the sky above Los Angeles freeways, it prompted officials in California to devise a plan that would reduce
C. birds had been overcome by pollution and routinely fell from the sky above Los Angeles freeways, prompting officials in California to devise a plan that reduced
D. birds overcome by pollution routinely fell from the sky above Los Angeles freeways, prompting officials in California to devise a plan to reduce
E. birds overcome by pollution and routinely falling from the sky above Los Angeles freeways were prompting officials in California to devise a plan to reduce



答案是D，但感觉句中没了主语，纠结中。。。

Karmalotse

有主语的啊，birds就是主语，birds(overcome by pollution)

routinely fell ...

masushuang

感谢好心人回答，对不起，写错了，想表达句中没动词
麻烦好心人再指点略微

zhuxiaocao

句子结构：
birds fell(谓语动词), prompting...