The correct option is A Chlorine
In electrolysis of sodium chloride, sodium ions move towards cathode and chloride ions move towards anode. There are bubbles formed on the surface of both electrodes when there is release a of sodiumnear cathode and chlorine gas near anode. The released chlorine gas is yellow in colour. Chloride is the ionic form and chlorine is the elemental form. So, the correct option is chlorine.