Appropriate tool for measuring curved path length

Steps:

• Identify the measurement needed: total length of a curved track about 0.5 m long.
• Note the track's shape: curved, requiring a flexible tool to follow the path.
• Evaluate options: rigid tools fail on curves; flexible ones succeed.
• Select tape measure: it conforms to irregular shapes for accurate path length.

Why D is correct:

• Tape measure is designed for linear measurements along flexible paths, allowing it to trace the curve's contour directly, unlike rigid straight-edge tools.

Why the others are wrong:

• A. Metre rule: rigid and suited only for straight-line distances, cannot follow curves.
• B. Micrometer: measures tiny thicknesses (e.g., 0.01 mm) precisely, not meter-scale lengths.
• C. Stop watch: measures time intervals, irrelevant for length.

Final answer: D