The study of origins and life of the planet earth is called

cell differentiation  is how generic embryonic  cells  become specialized  cells. this occurs  through a process called gene expression. gene expression is the specific combination of genes that are turned on or off (expressed or repressed), and this is what dictates how a  cell  functions.

explanation:

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.