| The total heating surface of any steam generating unit is comprised of which of the listed surfaces? |
| A) Those parts of a boiler which are exposed on one side to only the water being heated and on the other side to the combustion gases, such as the economizer surfaces. |
| B) Those parts of a boiler which are exposed on one side to only the steam being heated and on the other side to the combustion gases, such as the superheater surfaces. |
| C) Those parts of a boiler which are exposed on one side to the water or steam being heated, and on the other side to the combustion gases. |
| D) Those parts of a boiler which are exposed on one side to only the water being heated and on the other side being directly exposed to the furnace flame. |
