The work function for the photoelectric effect in potassium is 2.25 eV.For the case when light with a wavelength of 3.6 x 10-7 ；m falls on the potassium， the velocity of the fastest of the emitted electrons is（）

A.2.3X103； m/s

B.9.2X108 m/s

C.7.4X106； m/s

D.6.5X105； m/s

正确答案：6.5X105； m/s