Why can deciding workplace height only on the basis of an average person be risky in ergonomics?

Correct answer: Because real users may differ in height and reach

The direct answer is A: real users may differ in height and reach, so one average height may not suit everyone. Ergonomic design begins with the people who will actually use the workplace. Individuals differ in stature, arm length, strength, mobility, posture and task method. Step by step: identify the user group; measure or consider the range of body sizes; provide adjustment or choose a design that accommodates most users; then test comfort, reach and safety. Option A is correct because a fixed height based only on an average can force shorter users to stretch or taller users to bend. Option B is wrong because an average is a statistical summary, not a perfect size for every person. Option C is wrong because height strongly affects posture, reach and physical load. Option D is wrong because workplaces, users and tasks can change, so design should allow adaptation where possible. Memory cue: design for the range of users, not for an imaginary “average person” alone.