Statement (A): $\mathrm{\sigma }$ bond is present in molecule. 

Statement (B): In ethylene molecule, between two carbon atoms one bond and one bonds are present.  

Statement (C): In ethyne molecule, between two carbon atoms, one bond and two bonds are present.

In molecule mutual sharing of electrons between two hydrogen atoms axially to form bond.   

Ethylene and ethyne molecules are unsaturated hydro carbons.  Sufficient hydrogen atoms are not present to the valency of carbon atoms.  So carbon atoms form bonds.