A man can easily float on the water of the Dead Sea without sinking because

The average density of the human body with empty lungs is $1.07\text{g/cc}$  while lungs filled with air is $\text{1}\text{.00}\text{g/cc}$ 

In the Dead Sea, the density of water is $1.16\text{g/cc}$. That means the density of water in the dead sea is higher as compared to the average density of the human body. 

We know that when the density of the liquid is higher than the density of the object, the object floats in the liquid.

Therefore, option B is the correct answer.