Final answer:
The antonym for 'a person with a rigid viewpoint' is 'A person with a flexible viewpoint,' as it represents the opposite quality of being open to change and new ideas.
Step-by-step explanation:
An antonym for "a person with a rigid viewpoint" is "A) A person with a flexible viewpoint." Being rigid means being unwilling to change one's ideas or behavior, being inflexible. Conversely, a person with a flexible viewpoint is open to considering different ideas and is willing to adapt their thoughts or perspectives as needed.