Bank B Is a Correspondent of Bank A

Bank B is a correspondent of Bank A. Which of the following must be included in Bank A's calculation of credit exposure to Bank B?

A) A loan to Mr. Pierce from Bank A secured by Bank B common stock
B) Bank B's purchase of U.S. government T-Bills on behalf of Bank A under an overnight repurchase arrangement
C) Bank A's deposit account of $1 million in Bank B
D) A letter of credit issued by Bank B and pledged against the ACME Company's debt at Bank A