问题详情

Which of the italicized parts indicates UNCERTAINTY？

A．She can do it herself or ask someone else to do it.

B．The workers were cheerful, or at least they appeared to be cheerful.

C．They"ll stay here only a week or so.

D．Be careful, or you will break your neck.

请帮忙给出正确答案和分析，谢谢！