Question

The fact that current is uniform anywhere in a series circuit is an application of the principle of:

Answer 1

Due to the conservation of electric charge, the current is uniform throughout an electrical circuit.
The answer is B.

Answer 2

In series circuit there is no branching of the resistances

so here we know that all the resistors are connected without any branching and current will flow through all branches without any loss.

So here we know that current is defined as rate of flow of charge

$i = \frac{dQ}{dt}$

now here we can see that charge Q will flow at same rate through all the resistors which are connected in series

so here

$\frac{dQ}{dt} = constant$

so this will show the conservation of charge

so correct answer will be

conservation of charge