Why should a resistance be introduced in a circuit in series deliberately?

Explanation

In a series circuit, adding resistance is a way to control the current flow through the circuit. According to Ohm's Law, the current (I) is inversely proportional to the resistance (R) for a given voltage (V), i.e., I = V/R. By increasing resistance, the current can be reduced to safe levels, preventing potential damage or hazards. Option A is incorrect because increasing resistance does not increase current; it decreases it. Option B hints at a reduction in current but fails to include the broader concept of control. Option D is irrelevant, as the function of a resistor is not related to the appearance of the circuit.