I met a friend of mine _____ I was walking in the park. [ ]

A. because

B. after

C. when

D. if

具有清热凉血，利尿通淋，解毒疗疮功效的药物是：（）

A.白薇

B.青蒿

C.胡黄连

D.牡丹皮

E.黄柏