A precision measuring device used to measure linear dimensions, thickness, or diameter.

• A. Dial caliper
• B. Vernier caliper
• C. Micrometer
• D. Magnetic base

Answer: (A)

Measuring linear dimensions with a tool that gives a direct reading on a dial is the idea here. A dial caliper combines a main scale with a rotating dial indicator, so you can read outside dimensions, inside dimensions, and depths quickly and with good precision. That makes it well suited for checking thicknesses and diameters across a typical range, which fits the prompt.

A vernier caliper also measures these dimensions, but reading the vernier scale requires a little more interpretation, which can slow you down or introduce small reading errors. A micrometer offers higher precision but is best for very small features and specific close-in measurements, not as versatile for general thickness or diameter across a wider range. A magnetic base isn’t a measuring instrument itself; it’s a stand used to hold tools in place. So the dial caliper is the most fitting choice for precision measurements of linear dimensions like thickness or diameter.