A running man has half the kinetic energy of that of a boy of half of his mass. The man speeds up by 1 m/s so as to have same K.E. as that of boy. The original speed of the man will be
A. √2 m/s
B. (√2-1) m/s
C. 1/(√2-1) m/s
D. 1/√2 m/s