传染病流行过程的定义是（）

A.各种传染源不断向外界排出病原体

B.病原体侵袭易感者

C.病原体在中间宿主中的传代

D.病原体通过一定的传播途径，不断更迭其宿主的过程

E.病原体在宿主体内生长、繁殖的过程

In object-oriented (51) , objects can be viewed as reusable components, and once the programmer has developed a (52) of these components, he can (53) the amount of new coding required. But (52) a (54) is no simple task because the integrity of the Original software design is critical. Reusability can be a mixed blessing for user, too, as a programmer has to be able to find the object he needs. But if (55) is your aim, reusability is worth the risk.

A．complexity

B．creating

C．indisposing

D．library

E．maximize

F．minimize

G．reading

H．procedure

I．productivity

J．programming K. security L. using