If you see any type of cloud, you can expect fair weather.
~cirrus
~stratus
~cumulus
~nimbus

Option A, Cirrus

Explanation:

Let’s see all the given options one by one –  

1.Cirrus– These clouds are feathery clouds made up of ice. They represents a fair weather only in a clear blue sky

2.Stratus- There are flat clouds which cause steady rains.  

3.Cumulus – These are puff clouds and they do not grow tall (representing fair weather)  but when they grow tall they cause thunderstorm

4.Nimbus – These are dark colored clouds which are heavily loaded with water and cause precipitation in the form of rain, sleet, snow or hail

Thus option A, Cirrus is correct as it is most calm cloud.  

carbon atoms, hydrogen, oxygen, and nitrogen.