[单选题]
The mass of an atom q74mcslq wfnc77w e.4 ir.j5xnuy ,sgp n +ag94v 4)yw :kjpps vmr3;6ss
A. approximately equally divided between neutrons, protons, and electrons.
B. evenly divided between the nucleus and the surrounding electron cloud.
C. concentrated in the cloud of electrons surrounding the nucleus.
D. concentrated in the nucleus.
