Final answer:
The Supreme Court of the United States consists of one Chief Justice and eight Associate Justices, making up nine members in total.
Step-by-step explanation:
The question regarding the number of elected registrant members on a Board of Directors in 2021 cannot be specifically answered without more context about the organization in question. However, pertaining to the reference information provided about the composition of the Supreme Court, we can confirm that the correct answer is:
b. one chief justice and eight associate justices
The Supreme Court of the United States is composed of nine members in total. This includes one Chief Justice and eight Associate Justices, who are appointed by the President and confirmed by the Senate. They serve on the court for life, unless they resign, retire, or are removed after impeachment.