my suggestion is that your father () on at once,said the doctor calmly.be operated will be operated should operated

my suggestion is that your father () on at once,said the doctor calmly.
be operated will be operated should operated

选A
suggestion后面的从句中用原形动词,这里是被动,故选A.

be operated 因为有suggestion 所以从句需要用虚拟语气，即（should）+动词原形，这里的should可以省略，
望采纳，谢谢！