[单选题]
What happens to the kinetic energy of a speedy proton when its rela dfw rkc2j3 2++ouf)iotifmd+* 32a4tvl g5cjhnvistic mass doublevf aj mn+3gc5 t2l4h*ds?
A. It doubles.
B. It more than doubles.
C. It less than doubles.
D. It must increase, but it is impossible to say by how much.
