下列关于溃疡性结肠炎并发中毒性巨结肠的常见诱因错误的是（）

A.抗胆碱能类药物

B.使用吗啡

C.低血钙

D.全结肠镜检查

E.钡灌肠

I got up early that morning, but I _____ so because I had no work to do.

A．mustn’t have done

B．didn’t need to do

C．needn’t have done

D．can’t have done