___ clouds are formed in the upper atmosphere in clear skies and have a feather-like appearance.
With reference to Clouds, consider the following statements: 1. Cirrus clouds are formed at low altitudes. 2. Stratus clouds are layered clouds. 3. Nimbus Clouds are extremely dense and opaque to rays of sun. 4. Cumulus clouds exist in patches and can be seen scattered. Which of the above statement(s) is/are correct?