Answer: Option (A) is the correct answer.
Step-by-step explanation:
A closed circuit in which current is able to flow is known as a complete circuit.
In option (A), metal pin attached to the circuit is a good conductor of electricity. So, electric current will easily flow into the circuit. As a result, the circuit becomes complete.
In option (B), eraser is attached to the circuit and eraser acts as an insulator due to which electric current will not be able to flow into the circuit. As a result, circuit becomes incomplete.
In option (C), paper is attached to the circuit and it will also not let the current to pass through it as it is an insulator. Hence, the circuit becomes incomplete in nature.
Thus, we can conclude that out of the given options, diagram in option (A) illustrates a complete circuit.