The correct answer is A) Electric power and starting air. Explanation: Before performing any maintenance on a solenoid-operated air start valve, the electric power and starting air supply must be secured to prevent the valve from being activated unexpectedly, which could lead to serious safety hazards. Securing the electric power and starting air ensures that the valve cannot be operated during the maintenance work, allowing the technician to safely perform the necessary repairs or servicing. The other options are incorrect because they do not directly relate to the safe preparation for maintenance on a solenoid-operated air start valve. Securing the lube oil standby pump, control air, hydraulic switch, jacking gear, motor drain, and pneumatic control system power are not necessary steps for this specific maintenance task.