The correct answer is D. 400 kV.
Large industrial consumers are supplied electrical energy at 400 kV because this voltage is high enough to reduce losses in the transmission lines, but not so high that it is difficult to use in factories.
Option A, 400 V, is too low a voltage to be used for large industrial consumers. This is because the voltage drop in the transmission lines would be too high, and the power losses would be significant.
Option B, 11 kV, is a more common voltage for industrial consumers. However, it is still not high enough to be used for the largest industrial consumers.
Option C, 66 kV, is a higher voltage that is sometimes used for industrial consumers. However, it is not as common as 400 kV.
In conclusion, the correct answer is D. 400 kV.