In this passage, inertia means ______

A．a situation in which no action is taken

B．a situation in which no progress is made

C．the feeling of someone not wanting to move or do anything

D．the force making an object stay at rest or continue moving

传染病流行过程的基本条件是（）

A.病原体、人体和它们所处的环境

B.病原体、感菌动物、易感人群

C.传染源、传播途径、易感人群

D.传染源、传播途径

E.社会环节、自然环节