--- Why? Tom, your shirt is so dirty!

--- Mum, I ______ my storeroom downstairs.

A．cleaned

B．have cleaned

C．was cleaning

D．have been cleaning

下列哪些疾病适合做大规模的筛检（）

A.艾滋病

B.全民检查HBsAg

C.原位子宫颈癌

D.流行性感冒

E.麻疹