据媒体报道,我国因环境污染造成的巨大经济损失,每年高达6890000000元,这个数用科学记数法表示正确的是( ).(并保留2个有效数字)
6.9×109
To their great fear, they found________in the heaviest snowfall they had ever had. [ ]
A. they were catching
B. themselves caught
C. they had caught
D. themselves catching
能祛顽痰,通窍开闭,祛风杀虫的药物为()
A.细辛
B.天南星
C.旋覆花
D.郁金
E.皂荚