Solution:• Average salinity in Indian ocean is 35 per thousand. Normally low salinity is observed in bay of Bengal due to influx of large amount of freshwater from perennial run (Ganga Brahmaputra, Godavari, Krishna Kaveri, Kedong & also from seasonal river this causes the declining trend of salinity in Indian as we move towards Bay of Bengal from equator. So option B is correct.
• Salinity in Arabian Sea is higher than the Bay of Bengal because of relatively large evaporation then Bay of Bengal & less amount of rivers draining into it.
• 35‰ isohaline divides the ocean into eastern and western part so option A, C, D is wrong and B, E, is right.