The meaning of Yield to Maturity(YTM) is the annualized return an investor gets if he holds the bond till maturity. When we calculating such annualized return, a coupon or interest income, Reinvestment Income,the capital gain or loss till maturity is taken into account. YTM assumes that all copuns and principal repayment are made on the said date.

The term Yield to Maturity resembles, the yield that an investor gains over the maturity of the investment. It is the annulaized return by which future cashflows are discounted for the respective periods, the total of the discounted value of future cashflows exactly equals the present value of the bond or price of the bond. YTM is also known as Annual Percentage Rate.

Holding Period return means the return that is gained by the investor when he holds the bond for a period which is called holding period return. It is infact not in every case that bond investor will hold the bond till its maturity. If he is holding bond till its maturity, then his return will be equal to Yield to Maturity.

Hence option B that is when the bond is held till maturity is the correct answer.