HCl is considered as polar molecule and that is incorrect answer, The choices provided are A) HCl , B) CH₄ , C) H₂O, D) NH₃
And the correct answer is : B) CH₄
In case of H₂O and NH₃ the high difference in electronegativity between nitrogen or oxygen and hydrogen make the bonds acquire partial charges and become polar while in case of CH₄ the difference in electronegativity between carbon and hydrogen is only 0.4 so it considered as non-polar bond
also carbon connected from all directions with Hydrogens
YES LAW OF CONSERVATION OF MASS IS VALID DURING BECAUSE IT STATE THAT THE TOTAL MASS OF PRODUCTS MUST BE EQUAL TO THE TOTAL MASS OF REACTANT