84 When firing a boiler in local manual control, an increase in boiler load must be accompanied by a/an __________.

A. increase in the fuel oil flow before an increase in the forced draft pressure
B. decrease in the forced draft air pressure before a decrease in the fuel oil flow
C. increase in the forced draft air pressure before an increase in the fuel oil flow
D. increase or a decrease in the fuel oil flow and forced draft air pressure simultaneously