The circuit component which is used to close or break a circuit is:
A. Bulb
B. Switch
C. Wire
D. Cell

Hint: A circuit is made up of real components, power sources, and signal sources that are all linked together so that current can flow in a full circle.
A circuit is considered closed if the circle is complete and all currents have a path back to their origin. A circuit is said to be open if the circle is not full, or if there is a gap or opening in the path.

Complete step by step answer:
A switch is an electronic component that is used to close or open a circuit. It controls the flow of current in a certain arm of the circuit or the entire circuit.
Explanation: The most common type of switch is a manually operated electromechanical device that contains one or more sets of electrical contacts that are connected to external circuits.
> Each contact set can be in one of two states: "closed," which means the contacts are contacting and electricity can flow between them, or "open," which means the contacts are separated and the switch is non-conducting.
The symbol of an open switch is shown below:

The symbol of a closed switch is shown below:

The mechanism actuating the transition between these two states (open or closed) is typically (other types of actions exist) either a "alternate action" (flip the switch for continuous "on" or "off") or a "momentary action" (push for "on" and release for "off").
Hence, the correct option is: (B) Switch

Note:
Switching theory is concerned with the use of switches to create Boolean expressions and logic gates in the logic design of digital circuits. Switching theory enables us to comprehend the operation and relationship of Boolean Algebra and two-level logic functions in relation to Digital Logic Gates.