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
