---Did you go to school yesterday?

--- Yes, I did. But I was late. When I got to school, Mr. Zhang  __________his lessons.

A．has already begun

B．had already begun

C．has begun yet

D．had begun yet

患儿，8岁，跛行二天伴右下肢不适感，右膝痛，前来就诊，二天前，跳马后出现此症状。

如患儿右腹股沟肿胀，压痛（+），并沿股前放至膝部，右下肢假性长于左侧，X线片正常，应诊断为：（）

A.小儿弹响髋

B.扁平髋

C.小儿髋关节滑囊炎

D.儿童类风湿关节炎

E.股骨头骨骺炎