What is an energy resource

C) a natural resource that humans use to generate energy

So basically its anything found on earth to make energy. This includes nonrenewable sources such as fossil fuels (coal or natural gas), and renewable sources such as wind, hydro or solar.

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:

b. a lightning bug, plug of grass, and a worm