Answer:
Volcanic gases. (Ans A)
Step-by-step explanation:
Ocean water is salty because of the presence of dissolved salt. When water contact with a rock it starts weathering processes and this process starts to dissolve the soluble elements such as sodium out of the rock.
In volcanic gases, lots of chlorine ions are present in the atmosphere, these ions easily dissolve with water and produce the large flux of chloride that splashes into the oceans. So, the most common source of chloride ions in ocean waters comes from the volcanic explosions.