Final answer:
The disconnecting means for a submersible water pump must be within sight of the controller, to comply with the National Electrical Code for safety and accessibility purposes.
Step-by-step explanation:
For safety and compliance with the National Electrical Code (NEC), the disconnecting means for a submersible water pump must be within sight from the pump controller. The correct answer to the given question is, therefore, a. controller. This is important because it allows the power to the pump to be quickly shut off for maintenance or in case of an emergency. The NEC specifically requires that this disconnecting means be readily accessible and within sight, meaning it needs to be in the same room and within 50 feet of the controller, and without any intervening walls or barriers obstructing the view.