The correct answer is A) Cirrus. The cirrus cloud type is indicated by the number 1 in the illustration D039NG. Cirrus clouds are high-altitude, wispy clouds composed primarily of ice crystals. This cloud type is a key indicator for the Coast Guard Captain's License Exam, as it can signal the approach of a warm front and changing weather conditions. The other answer choices are incorrect because altocumulus (B) and altostratus (C) are mid-level cloud types, while nimbostratus (D) is a low-level, rain-producing cloud. The illustration clearly depicts the high-altitude, feathery appearance characteristic of cirrus clouds.