The correct answer is B) The high limit control secures power to the entire oil firing system. When the desired steam pressure is obtained in an automatically fired auxiliary boiler, the high limit control activates to shut off power to the entire oil firing system. This is a safety mechanism to prevent the boiler from producing excessive steam pressure. The other answer choices do not accurately describe the actions that take place in the control circuit under these conditions. Options A, C, and D describe different control mechanisms that may be present, but they do not specifically address the high limit control securing power to the oil firing system when the desired steam pressure is reached.