he insisted that we ___(be)backbefore 10 o'clock

insist
1、意思是“坚持要”表示命令、要求,其后之宾语从句要用虚拟式动词原形
或者“should + 动词原形”
例句：
I insist that you (should) be present.
They insisted that she (should) be invited.
I insist that you (should) see a doctor.
She insisted that he (should) go.
这种虚拟语气的用法除了“insist”还有：demand,suggest,order,propose.
2、意思是“坚持说,硬说”,其后宾语从句用普通时式,不用虚拟语气的哦.
例句：
She insisted that he was wrong.

should　be或be
insist表示＂要求＂时，从句要用虚拟语气即should+do而should是可以省略的．
谢谢

should