Why is it necessary to observe actual work before changing a workplace in ergonomics?

Correct answer: Because real movement posture and obstacles become clear through observation

The direct answer is A: real movement, posture and obstacles become clear through observation. Ergonomics improves a workplace by studying how the task is actually performed, not by guessing from a desk or a written description alone. Step by step: watch the worker perform the complete task; note reaching, bending, twisting, lifting, repetition and force; identify obstacles, awkward heights and unsafe movements; then choose a suitable change and check whether it helps. Option A is correct because direct observation reveals hidden risks and the difference between the planned task and the real task. Option B is false because observation provides useful evidence. Option C is unfair and false: workers may provide valuable information about discomfort and practical difficulties, even though observation is also needed. Option D is false because guessing can miss important risks. Memory cue: observe first, analyse the work, then improve the workplace.