What Is the Difference Between Yield-To-Maturity (YTM) and Realized Compound

What is the difference between yield-to-maturity (YTM) and realized compound yield (RCY) ?

A) They are actually the same concept.
B) YTM is the actual return, whereas, RCY is the expected return.
C) RCY is the actual return, whereas, YTM is the expected return.
D) YTM considers only coupon payments, whereas, RCY includes all a bond's cash flows.