题目选项分析

Since the 1970s, scientists have believed that

an asteroid once landed in the Gulf of Mexico and released ash causing a darkening of the sky by 10 to 20 percent over the ensuing decade, inhibiting photosynthesis and leading

Since the 1970s, scientists have believed that

an asteroid once landed in the Gulf of Mexico and that released ash was what caused a darkening of the sky by 10 to 20 percent over the ensuing decade, and it inhibited photosynthesis and led