Reader's question:  

Do some research ahead of time to know exactly what your item should look like. If a vendor only accepts cash, this is also a red flag.

Could you explain "red flag"

My comments:

Red flags are often used as a warning sign. In the old train station for instance, if there was something wrong preventing a train to enter or leave the station, sometimes a red flag was raised. If everything was alright, a green flag was waved.

In a public beach, when the waves are high or when, say, sharks are detected, red flags are sometimes put up to warn swimmers not to take to the water.

In the example from the top, the fact the vendor accepts only cash is described as "also a red flag" because the vendor might be operating what is called a fly-by-night operation – taking your cash in the morning and fleeing the city by nightfall.

This might not be the case of course but at least you're warned to take extra care. It pays. Better safe than sorry, as they say.

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本文僅代表作者本人觀點，與本網立場無關。歡迎大家討論學術問題，尊重他人，禁止人身攻擊和發布一切違反國家現行法律法規的內容。

Zhang Xin has been with China Daily since 1988, when he graduated from Beijing Foreign Studies University. Write him at: zhangxin@chinadaily.com.cn, or raise a question for potential use in a future column.