主管需要在月底前签署这些费用报告。

The supervisor needs to ___sign off on these expense reports by the end of the month.

他在邮件末尾用'祝好'作为结束语。

He ___signed off the email with 'Best regards'.

医生在完成手术后签字下班了。

The doctor ___signed off after finishing the surgery.