Which addition would be most beneficial to the following paragraph?

In the United States, it is a custom. Servers are paid a low hourly wage and rely on tips to make up the difference. Thus, regardless of the quality of the service, leaving a tip is a matter of common courtesy. However, in other parts of the world, servers receive a higher wage and tips are not expected. They are reserved only for exceptional service. In some locales, leaving a tip may even be considered insulting or rude.

Select one:
A. A clear topic sentence
B. Moew development
C. Transitional
D. Nothing. This paragraph requires no revision