Principal in Agency MBS securities is protected against default. Which of the following is a reason for the investors in Agency MBS to still take default assumption into account?

There is no reason for Agency MBS investors to care about default.

There is a high chance that the GSEs guaranteeing the principal will go out of business.

The recovered principal post default is repaid to investors in the form of prepayment.

Not all of the principal can be recovered even with the guarantee