What does the "proof" mean on a bottle of liquor? i know that 100 proof liquor is 50% alocohol and 80 proof is 40% and so on. but where does the term "proof" come from and why display it on the bottle? why not just say 50% alcohol etc etc?

i have no clue hope you find the answer

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.