Answer:
b) rivers
Step-by-step explanation:
Water near the mouths of rivers is not as salty as average sea water because river has less amount of salts as compared to sea water which has big reservoir of salts. The river water brings salts when this river passes through the mountains but the amount of salts are low while on the other hand, the sea water has huge amount of salts about 200 to 300 million years ago as a reservoir so we can say that water near the mouths of rivers is not as salty as average water of the sea.