The main difference between a series and a parallel circuit is that

a. more components can be added to a parallel circuit.

b. the voltage source for a series circuit can be weaker.

c. in a series circuit there's only one path for current to flow.

d. a parallel circuit can handle components with higher resistances.

C) is correct

series circuit - in the same path : current flow on one path so they are equal on each component and equal to the source's. voltage on each components may be different.

parallel circuit - between same nodes : voltage of the components are equal and equal to the source's. current on each components may be different.