伤寒致溶血尿毒症的机制是（）

A.免疫复合物沉着在肾小球基底膜造成急性肾功能不全

B.免疫复合物作用于红细胞膜，造成红细胞破裂出血

C.因伤寒菌血症引起骨髓炎和肾脓肿

D.伤寒杆菌内毒素诱发肾小球微血管发生凝血

E.伤寒杆菌内毒素破坏红细胞导致溶血

—Is your brother a League member?

—Yes, he____ the League three years ago. He____ a League member for three years

A．joined; has been

B．has joined; has been

C．was joined; is

D．joined; was