锥比
参考答案:底流口直径与溢流口直径比叫做锥比。
—What do you think of teaching, Bob?
—I find it fun and challenging. It is a job ______ you are doing something serious but interesting.
A.where
B.which
C.when
D.that
搞好个人卫生和环境卫生,消灭媒介生物,清除中间寄生生物和消毒工作是为了( )
A.控制传染源
B.保护易感人群
C.切断传播途径
D.消除病原体