red flag
成語所屬單字flag
red flag — 慣用語
1. a clear sign that something is wrong, dangerous, or likely to cause serious trou
1.慣用語
釋義
警訊；預警信號
a clear sign that something is wrong, dangerous, or likely to cause serious trouble.
例句
When the builder asked for full payment in cash upfront, that was a red flag for the family.
A sudden change in a child's eating habits can be a red flag for teachers and parents.