Answer: D.NaCl (aq)
Explanation: In Sodium chloride
Sodium atom has oxidation number of +1.
Electronic configuration of sodium:
Sodium atom will loose one electron to gain noble gas configuration and form sodium cation with +1 charge.
Chlorine atom has oxidation number of -1.
Electronic configuration of sodium:
Chlorine atom will gain one electron to gain noble gas configuration and form chloride ion with -1 charge.
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In sodium chloride the one electron from sodium metal gets transferred to chlorine atom to form ionic compound.
Ionic compounds dissociate to give ions when dissolved in water and thus are written as NaCl (aq).