$$NaHCO_3$$ is a mild alkali(salt of WA+SB) , it will easily react with strong organic acids like $$R-SO_3H$$ to give off $$H_2CO_3$$ which is unstable and breaks to $$H_2O + CO_2$$
Which isss
Gas A is $$CO_2$$
Gas B is $$ C^*O_2 $$, $$C^*$$ is C-14
Therefore (3) is correct.
