The correct answer is B parallel.
The two lamps in the diagram have two common points of connection. The potential difference across the two bulbs is the same and is equal to the potential difference across the battery. The current from the battery, splits into two at the common point of connection and flows into the bulbs. Such a connection is called parallel connection.The advantage of the parallel connection is that, if one of the bulbs fuses, the other continues to be lit with the same illumination.