Operable parts should require a maximum activation force of __________.

The correct answer is based on accessibility standards which dictate that operable parts must be easy to use for a wide range of individuals, including those with disabilities. The maximum activation force for operable parts, such as door handles, faucet controls, and other mechanical components, is set at 5 pounds. This standard ensures that the operable parts can be activated without excessive effort, making them accessible to individuals who may have limited strength or dexterity.

Design guidelines, including the Americans with Disabilities Act (ADA), emphasize usability in public and private facilities by establishing this limit. This requirement helps create an inclusive environment that accommodates all users, contributing to safer and more functional spaces. The other options do not meet the established criteria, as they either set the activation force too high, which could limit accessibility, or do not align with the recommended standards.