The sudden rapid fracture under stress (residual or applied) where the material exhibits little or no evidence of ductility or plastic deformation is called brittle fracture. This type of fracture is characterized by the material breaking without significant plastic deformation, making 'Brittle Fracture' the correct term.

409 stainless steel is classified as a ferritic stainless steel. Ferritic stainless steels are primarily composed of iron and chromium and are known for their good corrosion resistance and formability. Types such as 405, 409, 410S, 430, 442, and 446 are all part of this family, making option D the correct answer.

Low alloy steels are defined as steels which have up to 9% chrome content. This maximum level of chromium helps improve characteristics like high temperature strength and creep resistance, while remaining within the classification of low alloy steel.

885º F embrittlement, also known as sigma phase embrittlement, occurs predominantly in ferritic stainless steels such as the 400 series (which includes 410 SS and 430 SS) and duplex stainless steels like Alloy 2205. Austenitic stainless steels like the 300 series (including 308 SS) are generally not affected by this phenomenon. Therefore, the materials that can be affected by 885º F embrittlement include 410 SS, 430 SS, and Alloy 2205, making A, B, and D the correct options.

The threshold temperature for creep for the 5Cr-0.5Mo alloy is 800º F. This is the temperature at which the material begins to experience significant creep, which is a time-dependent deformation under stress at high temperature.