A mass of 10 kg is whirled in a horizontal circle by means of a string at an initial speed of 5 r.p.m. Keeping the radius constant, the tension in the string is quadrupled. The new speed is nearl
(A) 14 r.p.m.
(B) 10 r.p.m.
(C) 2.25 r.p.m.
(D) 7 r.p.m.