The best insulator is:

The best insulator from the provided options is Styrofoam, as it is made of expanded polystyrene, which has excellent thermal insulation properties. Styrofoam is lightweight, has a low thermal conductivity, and is often used in applications where maintaining temperature is crucial, such as in building constructions for insulating walls, roofs, and HVAC systems.

Its closed-cell structure traps air within its material, which significantly reduces heat transfer between the inside and outside of a structure. This makes it highly effective for both cold and hot conditions, helping keep indoor temperatures stable.

While blankets can provide warmth, their insulation capabilities can vary widely depending on the material they are made from. Batted insulation, often made from fiberglass, is also effective, but it typically does not match the performance of Styrofoam in situations that require low weight and high insulation. Aluminum, on the other hand, is a good conductor of heat and is generally used in reflective barriers rather than as an insulating material.