The correct option is Cirrus.
Explanation
Clouds are classified according to their height, expanse, density, and transparency or opaqueness. Based on altitude, they are grouped into high clouds, middle clouds, low clouds, and clouds with extensive vertical development.
Analysis of Cloud Types:
- Cirrus (High Altitude): These clouds are formed at the highest altitudes, typically ranging from 8,000 to 12,000 meters. They are thin, detached clouds with a feathery appearance and are always white in colour.
- Cumulus (Vertical Development): These clouds resemble cotton wool. They generally form at a height of 4,000 to 7,000 meters. They exist in patches and are characterized by a flat base.
- Stratus (Low Altitude): These are layered clouds that cover large portions of the sky. They are generally formed due to the loss of heat or the mixing of air masses with different temperatures and are typically found at lower altitudes (below 2,000 meters).
- Nimbus (Variable/Low): These are black or dark gray clouds. They form at middle levels or very near to the surface of the earth. They are extremely dense and opaque to the rays of the sun.
Key Takeaway: Cirrus clouds are the highest cloud type, forming between 8,000 and 12,000 meters, and are distinguished by their thin, feathery texture composed of ice crystals.