[单选题]
Doubling only the mass of apcklhb .b2(0t xd 8w7l vibrating mass-and-sprtbs*x l0y rv+mb+u- k*ing system produces what effect on the sbm+vuryt**0kbxl-+ system's mechanical energy?
A. increases the energy by a factor of two
B. increases the energy by a factor of three
C. increases the energy by a factor of four
D. produces no change