Proof resilience is the correct answer.

Proof resilience is a material property that represents the maximum amount of strain energy per unit volume that a material can absorb without permanent deformation or fracture. It is a measure of a material's ability to absorb energy and return to its original shape after being deformed.

To understand why proof resilience is the correct answer, let's first define the other options:

- Impact energy: Impact energy is the amount of energy that a body possesses due to its motion. It is not directly related to the maximum strain energy that can be stored in a body.

- Resilience: Resilience is the ability of a material to absorb energy when it is deformed elastically and then release that energy upon unloading. It is a measure of a material's ability to store and recover energy under elastic deformation. While resilience is related to strain energy, it does not represent the maximum strain energy that can be stored in a body.

- Toughness: Toughness is a measure of a material's ability to absorb energy and plastically deform before fracturing. It represents the total area under the stress-strain curve and is calculated by integrating the curve. While toughness is related to strain energy, it does not represent the maximum strain energy that can be stored in a body.

Proof resilience, on the other hand, specifically refers to the maximum strain energy that can be stored in a body. It is calculated as the area under the elastic portion of the stress-strain curve up to the yield point. The yield point is the point at which the material begins to deform plastically and permanent deformation occurs. The proof resilience represents the maximum energy that can be stored in a material without causing permanent deformation or fracture.

In summary, proof resilience is the correct answer because it specifically represents the maximum strain energy that can be stored in a body without permanent deformation or fracture. Impact energy, resilience, and toughness are related concepts but do not represent the same property as proof resilience.