15.3　THETONEOF PUBLIC SIGNS

When you are creating a public sign，you are writing either to enact suitable behavior in public or to inform the public of their obligations or privileges.Therefore，the tone of public signs should be both persuasive and instructive.(https://www.daowen.com)

The message in a public sign should be conveyed in such a manner that it would be helpful in the building of public comity.For this reason，it should also be conveyed in a polite tone.It can be realized by the frequent use of the courteous words like“please”and“thank you”.