Final answer:
Cirrus clouds (option A) are thin, wispy clouds found high in the atmosphere, and they are composed of ice crystals.
Step-by-step explanation:
The clouds that are thin and wispy and occur high in the atmosphere are known as cirrus clouds. These clouds are typically found at altitudes above 20,000 feet (6,000 meters) and are composed of ice crystals. The appearance of cirrus clouds is often described as hair-like or feathery, which differentiates them from other types of clouds.
Unlike cirrus, cumulus clouds are often denser, with a fluffier appearance, and are a result of convection. Stratus clouds are typically lower, blanket-like cloud layers, while stratocumulus clouds combine characteristics of stratus and cumulus, generally appearing in large, dark, rounded masses.
Hence, the correct answer is Option A.