A customer buys stock in an existing margin account, and fails to meet the Regulation T call within the specified maximum $4$ business day limit$.$ The action that may be taken is: A the broker$-$dealer can request an extension for payment from the FRB B the broker$-$dealer can sell securities from the account in an amount to satisfy the call C the customer can sell "short against the box" enough securities held in the account to meet the Regulation T call D the entire account must be liquidated