It is required to cut screw threads of 2 mm pitch on a lathe. The lead screw has a pitch of 6 mm. If the spindle speed is 60 r.p.m., then the speed of lead screw will be

A. 10 r.p.m.

B. 20 r.p.m.

C. 120 r.p.m.

D. 180 r.p.m.

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