Which of the following italicized phrases indicates reason？A．It"s a machine for slicing br

Which of the following italicized phrases indicates reason？

A．It"s a machine for slicing bread.

B．He was sent to prison for robbery.

C．Passengers for Tianjin must change at Ben"ing.

D．The shop sent me a bill for $50.

请帮忙给出正确答案和分析，谢谢！