How should the electric lamps be connected with the mains so that the switching on or off a lamp has no effect on other lamps?
A. In parallel
B. In series
C. In series and parallel both.
D. none of these.

Hint: We have studied in current electricity that in series circuit combination, the source voltage is the sum of the voltage drops at every load connected in the circuit but while in the parallel combination, the current flowing through each load is different, but the voltage across each load is same.

Complete step by step answer:
The power of a lamp when connected in parallel combination is given by:
$P = \dfrac{{{V^2}}}{R}$
Here, P is the power, V is the voltage across the lamp, and R is the lamp's resistance.
We generally connect home appliances in the parallel circuit. Parallel circuiting is also done with the electric lamps because when appliances along with the lamps are connected in parallel, the working of one of the appliances will not affect the other appliance. A lamp connected in parallel would have a different fuse. If one of the appliances is cut off in parallel, then the second appliance will remain in working condition.
Therefore, when the electric lamps are connected with the mains in parallel combinations, there is no effect on the other lamp.

So, the correct answer is “Option A”.

Note:
We must keep in mind that the parallel circuit combinations are quite advantageous in power saving. Two 5V batteries connected in series will not be more efficient than two five-volt batteries connected in parallel. The 5 V batteries connected in parallel would run twice as long as two 5V batteries are connected in series.