**Explanation:**

When an inductor has zero initial current (i.e., no current flowing through it) at time t=0, it acts as an open circuit. This means that there is no continuous path for the flow of current through the inductor.

**Reasoning:**

The behavior of an inductor is described by the relationship between the voltage across it (V) and the current flowing through it (I), known as the inductor equation:

V = L * di/dt

where L is the inductance of the inductor and di/dt represents the rate of change of current with respect to time.

When there is no initial current (I = 0) at t = 0, the derivative of current with respect to time (di/dt) is also zero. Therefore, according to the inductor equation, the voltage across the inductor is also zero.

In practical terms, this means that the inductor behaves as an open circuit. An open circuit is a circuit element that does not provide a continuous path for the flow of current. It effectively blocks the flow of current through it.

**Example:**

Consider a simple circuit consisting of a voltage source (V) and an inductor (L) connected in series. If the inductor has zero initial current (I = 0) at t = 0, the voltage across the inductor is also zero.

Since the voltage across the inductor is zero, there is no potential difference to drive the flow of current through it. As a result, no current flows through the inductor, and it acts as an open circuit.

This behavior can be understood intuitively by considering the inductor as a coil of wire. When there is no current flowing through the coil, there is no magnetic field generated, and hence no back-emf is induced. Consequently, the inductor does not oppose the flow of current, and it behaves as an open circuit.

Therefore, the correct answer is option B - an inductor with zero initial current acts as an open circuit.