思密达对何种毒素有固定作用 （）

A.大肠杆菌毒素

B.铜绿假单胞菌毒素

C.金黄色葡萄球菌毒素

D.霍乱毒素

E.流感毒素

Beijing ______ some strong winds, with dust blowing at 20 meters per second in the capital these days.

A．sees

B．saw

C．is seeing

D．was seeing