Correct option is D
Slip gauges (gauge blocks) are precision measuring tools used to achieve highly accurate length measurements. They are joined together through a process called "ringing", where two slip gauges adhere to each other without any adhesive due to molecular attraction and surface tension.
Ringing process:
1. The surfaces of the slip gauges are wiped clean to remove dust and oil.
2. The gauges are pressed together and slid slightly in a circular or wringing motion.
3. The extremely flat and smooth surfaces create a vacuum and molecular adhesion, holding them firmly together.
4. This allows stacking of multiple slip gauges to achieve precise measurements.
