Average salinity of water of Arabian Sea is
Think of Salinity as a book you have already read. On the page about Average salinity of water of Arabian Sea, the name written there is 35 ppt. That is the whole answer. No trick here. Just a simple fact that you can recall in a few seconds.
Ref: [53rd to 55th BPSC (Pre) 2011] | NCERT Geography textbooks and Goh Cheng Leong, Certificate Physical and Human Geography, discuss Salinity and explain the geographical concepts and processes that support the correct answer for this question.