Answer:
voltage available to each light remains constant regardless of the number of lights that are on.
Step-by-step explanation:
As per the circuit diagram all the four bulbs are connected in parallel with the source of voltage
so here when two or more components are connected in parallel then we can say that the potential difference across all the components will remain same.
So we can say that here potential difference across all the bulbs will be same while total current drawn from the cell is sum of the current in each bulb
So we will have

so if we add more bulbs in parallel then the current will be more drawn from the battery
Also if we add more bulbs in parallel then the resistance of the circuit will decrease.
So correct answer will be
voltage available to each light remains constant regardless of the number of lights that are on.