问题补充：
I insisted that a doctor immediately.
A. has been sent for
B. sends for
C. be sent for
D. will be sent for
答案：
A. has been sent for
B. sends for
(答案→)C. be sent for
D. will be sent for
解析：考查虚拟语气。句中insist作“坚持要求”，从句用should + v原形，should可以省略。句意：我坚持要求立即去请医生。
