Advertising is different from other forms of communication in that the advertiser pays for the message         .

A．to deliver

B．having delivered

C．to be delivered

D．delivering

外伤性血胸胸腔内积血不凝固，这是因为（）

A.胸腔内有抗凝物质

B.胸腔内渗出液体的稀释作用

C.肺、膈肌运动的去纤维化作用

D.凝血因子减少