What Is a "Power of Sale" in Connection with a Mortgage

What is a "power of sale" in connection with a mortgage?

A) It is a statute allowing the secured property to be sold in order to satisfy the related debt if it is not paid according to the stated terms.
B) It is a provision in a mortgage or deed of trust that allows a foreclosure process that does not involve court action.
C) It is a provision in a mortgage or deed of trust that allows the borrower to sell the property even though the loan associated with the mortgage has not been paid off.
D) It is the general principle that a mortgage or deed of trust cannot take away the borrower's legal right to sell property whether or not there is a security interest associated with it.