Answer;
D. Bourdon gage—indicate steam pressure in a furnace
Step-by-step explanation;
-Steam boiler or furnaces use pressure gage to measure pressure at some places either for water fluid or steam fluid. The pressure gages includes Bourdon pressure gage, bellow pressure gage and the spiral pressure gage.
-The bourdon pressure gage is type pressure gage which has bourdon tube, (an oval cross section of hollow tube). The tube has two ends, open and close. Open end is connected to fluids either water or steam and close end is connected to mechanical linkage in gage pointer. When the pressure builds up, the bourdon tube will be straightened out.