In a Rutherford scattering experiment when a projectile of change `Z_(1)` and mass `M_(1)` approaches s target nucleus of change `Z_(2)` and mass `M_(2)`, te distance of closed approach is `r_(0)`. The energy of the projectile is
A. directly proportianla to `M_(1)xxM_(2)`
B. directly proportianla to `Z_(1) Z_(2)`
C. directly proportianla to `Z_(1)`
D. directly proportianla to mass `M_(1)`