Do you have any idea of the reason _____ he referred to？

A．that

B．where

C．why

D．when

关于克雷白杆菌肺炎，下列正确的是

A．起病急，胸痛，畏寒

B．咳嗽，咳红棕色胶冻样痰

C．外周血白细胞正常或增加

D．青壮年多见，预后良好