超抗原的作用特点是()

A．不需要APC加工处理

B．TCRVβ区结合

C．有MHC限制性

D．一端与MHCⅡ类分子抗原结合槽外侧结合

E．以完整蛋白质分子发挥作用

— How long has your brother been working in this factory?

— 　　　 he graduated from college.

A．When

B．By the time

C．Until

D．Ever since