The correct answer is C) single-pass, fire-tube, scotch marine. The description of "single-pass, fire-tube, scotch marine" accurately matches the type of boiler shown in the illustration. A scotch marine boiler is a type of fire-tube boiler where the hot gases from the furnace pass through the boiler only once before exiting, making it a single-pass design. This type of boiler is commonly used on smaller vessels. The other answer choices do not fit the description of the boiler in the illustration. A two-pass, water-tube boiler, a two-pass, scotch marine boiler, and a forced circulation, coil-type boiler have different designs and characteristics that do not match the provided information.