Coupon payments are fixed, but the percentage return that investors receive varies based on the market conditions. this percentage return is referred to as bonds yield.

Yield to Maturity (YTM) is the rate of return expected from a bond held until its maturity date. However, the YTM equals the expected rate of return under certain assumptions. which of the following is one of these assumptions ?

(a)The probability of default is zero

(b)The bond is callable