Step-by-step explanation:
1) The main constituting element in paper , diamond and cloths is carbon atom.This because carbon atom has unique property of creating strong covalent bonds with other carbon atoms which give rises to complex organic structures.
2) There two oxides formed by carbon which are : carbon-dioxide
and carbon monoxide CO.
Structure are given in an image.
3) In molecule of methane there is a 1 mol of carbon.
Methane =

In 1 molecule of ethene there are two carbon atom double bonded to each other.
Ethene =

Electron dot structure of methane and ethene are given in an image