Which one of the following statements is TRUE?

Holes of diameter $${25.0^{\matrix{ { + 0.040} \cr { + 0.020} \cr } }}\,\,mm$$ are assembled interchangeably with the pins of diameter $${25.0^{\matrix{ { + 0.005} \cr { + 0.008} \cr } }}\,\,mm.$$

The minimum clearance in the assembly will be

Which one of the following instruments is widely used to check and calibrate geometric features of machine tools during their assembly?

The flatness of a machine bed can be measured using