_____ to sunlight for too much time will do harm to one's skin. 

A．Exposed

B．Having exposed

C．Being exposed

D．After being exposed

黄体酮治疗先兆流产，必须肌肉注射给药其主要理由是

A．口服吸收缓慢
B．口服后在消化道和肝内迅速破坏
C．口服用药排泄快
D．肌肉注射吸收迅速
E．注射用药能维持较高浓度