Correct Answer - Option 2 : 40 A

__Concept:__

In a transformer with a kVA rating of S,

The primary current \({I_1} = \frac{S}{{{V_1}}}\)

Secondary current \({I_2} = \frac{S}{{{V_2}}}\)

Where V_{1} is the primary voltage

V_{2} is the secondary voltage

__Calculation:__

Given that, kVA rating of transformer (S) = 4 kVA

Primary voltage (V_{1}) = 100 V

Secondary voltage (V_{2}) = 200 V

Primary current

\({I_1} = \frac{{4 \times {{10}^3}}}{{100}} = 40\;A\)