Company A is a start-up company, they only have less than 20 personnel. The treasury function maintains the custody of funds, investments and the record-keeping of cash and investment related transactions. Which of the following compensatory control should be employed in the absence of segregation of duties?

a. The treasurer handling the transaction should periodically reconcile the cash book and investment records.

b. The transactions should be properly authorized by the CFO.

c. An accounting supervisor should review the cash and investment related entries posted in the company's books.

d. The treasurer should maintain the certificates of investments in a safety deposit box.