Which is a limit on the way political action committees can raise money when they are branches of labor unions or professional organizations?

The answer is B) They can only raise money from their members

This political action committees need to be regulated in order to function properly and ethically.

By putting up such restrictions, the government can make sure that these labor unions and professional organizations are able to represent the interests of a certain group of people and businesses.

It, therefore, also helps to promote these political action committees as a reliable and a democratic way to voice legitimate concerns of businesses and individuals.