(b) 30-35%

Explanation:

Sea water typically has a salinity of around 35 g/kg although lower values are typical near coasts where river enter the ocean. Rivers and lakes can have a wide range of salinities, from less than 0-0.1 g/kg to a few g/kg, although there are many places where even higher salinities are found. The dead sea has a salinity of more than 200 g/kg.