What Is the Primary Distinction Between Mortgage-Related Securities Backed by Residential

What is the primary distinction between mortgage-related securities backed by residential mortgages and those backed by commercial mortgages?

A) Default is the key risk with residential mortgages; prepayment is the key risk with commercial mortgages
B) Interest rate risk is the key risk with residential mortgages; prepayment is the key risk with commercial mortgages
C) Prepayment is the key risk with residential mortgages; default is the key risk with commercial mortgages
D) Prepayment is the key risk with residential mortgages; interest rate risk is the key risk with commercial mortgages