Explanation:

First option is incorrect. Cumulonimbus clouds are a type of cumulus cloud associated with thunder storms and heavy precipitation. They are also a variation of nimbus or precipitation bearing clouds. Cumulonimbus clouds are also known as thunderheads due to their unique mushroom shape.
Second option is incorrect. Cumulus clouds are puffy clouds that sometimes look like pieces of floating cotton. The base of each cloud is often flat and top of the cloud has rounded towers.
Third option is also incorrect. Altostratus is a middle altitude cloud genus belonging to the stratiform physical category characterized by a generally uniform gray to bluish-green and sheet or layer.
Fourth option is correct. Cirrus clouds are formed at high altitudes. They are thin and detached clouds having a feathery appearance. They are always white in colour.