E7D15:What is the purpose of a step-start circuit in a high-voltage power supply?

Direct answer summary (2024-2028 NCVEC pool)

The official correct answer for E7D15 is To allow the filter capacitors to charge gradually.

The key fact is To allow the filter capacitors to charge gradually. Match that fact to the exact condition in the question; the other choices describe a different rule, band, component, or operating situation.