The correct answer is C) 5 years from the date of manufacture. This is the correct answer because the standard shelf life for an unbroken filter gas mask canister is 5 years from the date of manufacture, as per the regulations and standards set by the US Coast Guard for approved safety equipment. The canister's filter media and seals are designed to maintain their integrity and effectiveness for up to 5 years when the original packaging is intact and the canister has not been opened or used. The other options are incorrect because 1 year (A) is too short, and 3 years (B) or 7 years (D) do not align with the established 5-year shelf life requirement for this type of safety equipment.