____ is mentioned above, the number of the cattle here has been limited to 200.

A．It

B．Which

C．That

D．As

过敏性紫癜的表现以下哪项有特征性（）

A．可出现腹痛，便血

B．反复出现对称性皮肤紫癜

C．起病前1～3周常有上呼吸道感染史

D．可出现血尿和蛋白尿

E．可累及大关节