I heard it was going to become cloudy this afternoon, ____ by a storm.

A．following

B．followed

C．follow

D．to follow

据研究，地面上空h（m）处的气温t（℃）与地面气温T（℃）有如下关系：t=T-kh，现用气象气球测得某时离地面150（m）处的气温为8.8℃，离地面400（m）处的气温为6.8℃，请你估算此时离地面2500（m）高空的气温是（　　）

A．-10℃

B．-15℃

C．-20℃

D．-25℃