The correct answer is C. Patron.
A patron is a person who supports a cause or organization financially or through other means. A guardian is a person who is legally responsible for the care of another person, such as a child or a person with a disability. A saint is a person who is believed to be holy and who is often venerated by religious people. A friend is a person who you like and trust and who you enjoy spending time with.
Patron is the best synonym for benefactor because it is the most specific. A patron is someone who supports a cause or organization, while a guardian, saint, or friend can support a person. Additionally, a patron is typically someone who is wealthy or powerful, while a guardian, saint, or friend does not need to be.