The best answer is B. Member firms are permitted to set their own levels of margin for customers to sell naked options - both initial and minimum margins. These can be the same as, or higher, than regulatory requirements, but never lower. For example, the margin to sell a naked call is set by Regulation T at 20% of the market value of the stock, with a 10% minimum requirement. The member firm could set its own levels at 30% and 20% respectively.
Note that the dollar margin requirement are determined by percentages, as well as a flat dollar minimum. For example, the member firm could state that while minimum equity to open an account is set by FINRA and the CBOE at $2,000, the firm wants $10,000 of equity minimum to open an account that will sell naked options. A flat dollar minimum cannot be based on account activity, because this must be a uniform amount for all such accounts.