37) Pick the material which has the least coefficient of thermal expansion

38) What is the relation between the lead (L) and pitch (P) of a two start thread screw?

39) Identify a solid lubricant?

40) In which machining process, large amount of material is removed?

41) Name the fit, in which the shaft is cooled below the room temperature until it fits into the hole, then assembly is allowed to attain room temperature.