After living in America for over 20 years, Brother Sway said to a reporter the other day, “I ________ done bigger things, had bigger achievements had I stayed in China.” .

A．must do

B．could do

C．could have done

D．must have done

在反射活动中，最易发生疲劳的部位是（）

A.感受器

B.传入神经

C.反射中枢

D.传出神经

E.效应器