Question

Explain the proverb"All doors open to courtesy"

Answer 1

The quote is "All doors open TO courtesy." This means that people will go out of their way to help anyone who is polite. 

Answer 2

“All doors open to courtesy.” Courtesy means nothing but etiquette. Greeting others, without any distinction like servant, master, maid, watchman, manager, etc. is a distinguished feature to be maintained among human beings.

If we are polite to others, then we will be treated properly. If we want to make something happen, it will happen easily if we ask in a polite manner. If we are rude to others it will simply create issues and that work never happens. So, politeness paves a way to work done.