=()
A.
B.
C.
D.
参考答案:A
解析:
This is _______ empty bottle. But it is _______useful one.
A.a; a
B.an; a
C.an; the
D.a; an
人体与病原体处于相持状态,不出现临床症状,不排出病原体
A.病原体被消灭或排出体外B.病原体携带状态C.隐性感染D.潜在性感染E.显性感染