—Why are you so busy, Mike ?

—I ______ a novel these days.

A．was writing

B．wrote

C．am writing

D．have written

胸水、腹水等标本含菌量通常较少，为提高阳性检出率不可采用如下哪种方式处理（）

A.溶解

B.离心

C.过滤浓缩

D.采集较大量标本

E.37℃保藏24小时后接种培养