The two factors in bond markets that lead to a positive risk premium are $($Check only two.$)$

Choice $1$ of $4$:A$.$ The probability of default.

Choice $2$ of $4$:B$.$ The variability of inflation expectations.

Choice $3$ of $4$:C$.$ Bondholders' degree of risk aversion.

Choice $4$ of $4$:D$.$ The length of time over which payments are made