在“研究凸透镜成像”实验中，为了使烛焰的像能成在光屏的中间，首先要调整______和______高度，使它们的中心跟烛焰的中心大致在______．实验时先固定______的位置，然后调整______的位置，最后移动______，直到光屏上出现清晰的烛焰的像．

All the doctors in the hospital insisted that he ___________ badly wounded and that he ______ at once. [ ]

A. was; be operated on

B. should be; be operated on

C. were; must be operated on

D. was; should be operated