The correct answer is $\boxed{\text{D}}$, 60 V.
The voltage ratio of a transformer is given by the equation:
$$\frac{V_p}{V_s} = \frac{N_p}{N_s}$$
where $V_p$ is the primary voltage, $V_s$ is the secondary voltage, $N_p$ is the number of turns in the primary coil, and $N_s$ is the number of turns in the secondary coil.
In this case, we are given that $N_p/N_s = 2$ and $V_p = 120 \text{ V}$. Substituting these values into the equation, we get:
$$\frac{V_p}{V_s} = \frac{N_p}{N_s} = 2$$
$$V_s = V_p \cdot \frac{N_s}{N_p} = 120 \text{ V} \cdot \frac{1}{2} = 60 \text{ V}$$
Therefore, the secondary voltage is 60 V.
Option A is incorrect because the secondary voltage cannot be 0
V. This is because the transformer is a passive device, and it cannot create energy. The secondary voltage can only be less than or equal to the primary voltage.Option B is incorrect because the secondary voltage cannot be 36 V. This is because the voltage ratio is 2, and the secondary voltage is always less than or equal to the primary voltage.
Option C is incorrect because the secondary voltage cannot be 40 V. This is because the voltage ratio is 2, and the secondary voltage is always less than or equal to the primary voltage.
Option E is incorrect because the secondary voltage is not none of the above. The secondary voltage is 60 V.