The Term 'Default Risk Structure of Interest Rates' Refers to the Fact

The term 'default risk structure of interest rates' refers to the fact that:

A) there is a premium due to uncertainty about the future level of interest rates.
B) interest rates for different maturity ranges are determined independently.
C) at any point in time as the probability of default increases,the required yield on debt decreases.
D) at any point in time as the probability of default increases,the required yield on debt increases.