Answer :
The correct tool to calibrate a micrometer or check its accuracy is a gauge block, which serves as a precise reference standard for calibration. The correct answer is a.
The tool that is generally used to calibrate a micrometer or check its accuracy is a gauge block. Gauge blocks are precision ground and lapped to specific thicknesses and are used as a reference standard for the calibration of measuring equipment. A gauge block provides a precise reference dimension that the micrometer can be adjusted against to ensure it is giving accurate readings.
Tools like vernier calipers or dial indicators are also precise measuring instruments, but they involve their own potential for error and are generally not used as calibration references for other measuring tools like micrometers. On the other hand, feeler gauges, while used for measuring gaps and clearances, are not suited for micrometer calibration. The correct answer is a.
