Correct Option
The correct option is (c) 2 and 3 only.
Explanation
Salinity is the amount of salt in grams present in 1,000 grams of water. It is usually expressed as parts per thousand (ppt). The salinity of water bodies varies significantly depending on evaporation, precipitation, and the influx of fresh water.
Statement-wise Analysis
- Statement 1 is Incorrect. The average salinity of the oceans is approximately 35 parts per thousand (35 ppt), not 10 parts per thousand. While salinity can vary slightly between different oceans (typically ranging from 33 to 37 ppt), 10 ppt is characteristic of brackish water, not open ocean water.
- Statement 2 is Correct. The Dead Sea in Israel is a hypersaline lake with a salinity of approximately 340 grams per litre (340 ppt). This extremely high salt concentration increases the density of the water, allowing swimmers to float easily.
- Statement 3 is Correct. River water contains small amounts of dissolved salts. These salts are derived from the weathering of rocks and soil erosion as water flows over land. Although the concentration is low (usually less than 0.5 ppt, classifying it as fresh water), it is not devoid of salts.
Key Takeaway: The average salinity of the world's oceans is 35 parts per thousand. Hypersaline bodies like the Dead Sea have much higher salinity (approx. 340 ppt), while fresh water contains trace amounts of dissolved salts.