A mutual mistake exists when both parties to the contract ha

A mutual mistake exists when both parties to the contract have an erroneous assumption about the same important fact. When both parties are indeed mistaken about the same important fact, the resulting contract can be avoided if:
The mistake relates to a basic assumption upon which the contract was made
The mistake relates to an intrinsic fact that is material to the contract
The party adversely affected by the mistake did not bear the risk of the mistake
All of the choices are correct.

Solution

All of the choices are correct.

When both parties are indeed mistaken about the same important fact, the resulting contract can be avoided if the mistake relates to a basic assumption upon which the contract was made, the mistake relates to an intrinsic fact that is material to the contract and the party adversely affected by the mistake did not bear the risk of the mistake. Hence the correct answer is All of the choices are correct.