Question 5 is based on the following graph.

Drug X, which kills on contact the bacteria that cause the infection, is administered to patients by means of an aerosol inhaler.
Which of the following, if true, contributes most to explaining the change in drug X’s effectiveness during the course of the infection

属于局部式空调系统优点的是（）。

A．空调房间之间无风道相通

B．冷冻机和通风机直接设置在空调房间或临室内

C．不需要空调机房

D．机组分散