下列属于实践活动的是                                           （   ）

①小明在教室认真听课

②科学家向“嫦娥一号”发出指令撞击月球

③农民应用知识科学种田

④医生奋战在抗击甲型H1N1流感一线

A．①②③

B．①②④

C．①③④

D．②③④

In the Northern Hemisphere a wind is said to veer when the wind（）.

A.Changes direction clockwise，as from north to east，etc

B.Changes direction violently and erratically

C.Remains constant in direction and speed

D.Changes direction counterclockwise，as from south to east，etc