The correct answer is A) single-pass, fire-tube, scotch marine. The illustration provided depicts a single-pass, fire-tube, scotch marine boiler. This type of boiler is commonly used on smaller vessels, including those operated by the US Coast Guard. The fire-tube design and single-pass configuration are the key features that identify this boiler as a scotch marine type, which makes option A the correct choice. The other options are incorrect because they describe different boiler types that do not match the illustration. Option B describes a forced circulation, coil-type boiler, option C describes a two-pass, scotch marine boiler, and option D describes a two-pass, water-tube boiler, none of which match the characteristics of the boiler shown.