The correct option is B hydrogen gas
Hydrogen gas results in the cathode product while electrolysis of a dilute solution of sodium chloride.
At cathode, two reduction reactions compete with each other. One is reduction of Na(I) ions to Na
Na++e−→NaEored=−2.71V
The other reaction is the reduction of water to hydrogen gas.
22O+2e−→H2+2OH−Eored=−0.83V
The standard reduction potential for the reduction of water is higher than that for reduction of Na+
Water has much greater tendency to get reduced than Na+ ions. hence, the reduction of water to liberate hydrogen is the reaction at cathode for the electrolysis of aq NaCl.