Final answer:
According to the information provided, half of the members of Congress are millionaires.
Step-by-step explanation:
According to the given information, currently about half of the members of Congress are millionaires. Therefore, the correct answer to the question is a) Millionaires. It is important to note that this information is specific to the members of Congress and may not represent the entire Senate. Also, the inclusion of other professions such as businessmen, doctors, or lawyers cannot be confirmed based on the given information.