求助700-800的一道题，很困惑。。。逻辑主语相关，官方解答解释不了我的疑惑

zzy0429

Carbon monoxide levels in the atmosphere grew by enough of an increased percentage during the twentieth century that it began to trap heat radiating from the Earth, and it caused the average surface temperature to rise.
• Carbon monoxide levels in the atmosphere grew by enough of an increased percentage during the twentieth century that it began to trap heat radiating from the Earth, and it caused the average surface temperature to rise.
• Carbon monoxide levels in the atmosphere increased by enough of a percentage during the twentieth century that they began to trap heat radiating from the Earth, causing the average surface temperature to rise.
• Levels of atmospheric carbon monoxide increased sufficiently during the twentieth century to begin trapping heat radiating from the Earth, causing the average surface temperature to rise.
• Atmospheric carbon monoxide levels increased by a sufficient percentage during the twentieth century to begin trapping heat radiating from the Earth, which caused the average surface temperature to rise.
• Levels of carbon monoxide in the atmosphere during the twentieth century increased enough to begin trapping heat radiating from the Earth, causing the average surface temperature to rise.

这道题答案是C,但是levels可以做begin trap的主语吗？难道不是carbon monoxide做begin trap的主语。。。。
levels increased to begin traping...怎么看都不对啊

HoganTong

lz纠结的是level不能trap对吧？正因为level不能trap，所以才要选C这种to verb的结构，把trap用作宾语补足语，而不是宾语。

老白在费城

虽然我也觉得有点奇怪，但是五个选项都是carbon monoxide level作主语，所以LZ不用纠结了。。。