Answer:
b. Decreases
Step-by-step explanation:
The total resistance of a series circuit is equal to the sum of the individual resistances:
(1)
Therefore, as we add more lamps, the total resistance increases (because we add more positive tems in the sum in eq.(1).
The current in a circuit is given by Ohm's law:
![I=(V)/(R_T)](https://img.qammunity.org/2020/formulas/physics/high-school/ahwjpncu293h2o2sttmiu2ck4kqwh6k4ot.png)
where V is the voltage provided by the power source and
is the total resistance. We notice that the current, I, is inversely proportional to the total resistance: therefore, when more lamps are added to the series circuit, the total resistance increases, and therefore the current in the circuit decreases.