I think it is B ?

10. Which of the following best defines the bid-ask spread? e difference between the price at which a bond is issued and at which it trades B. The difference between the price a bond dealer is willing to pay to buy and the price at which he or she is willing to sell C. The difference between the price at which a bond can be called and its current price D. The sum of the price at which a bond dealer is willing to pay to buy and the price at which he or she is willing to sell