Read the following passage carefully and answer the question (Q. Nos. 1 to 4) choosing the correct alternatives:

Man does not live by food alone. Whereas, we can do for weeks without food,we cannot live without water longer than a couple of days. Water is vital to human health and fitness. Although it is not a nutrient as are carbohydrates, fats, proteins, vitamins and minerals, it, infact, is a key nutrient as no life is possible without it. Water approximates 60 percent of the body weight of human adults. It is an exellent solvent-more substances are soluble in water than in any other liquid known so far. This makes it an ideal constituent of the body fluids which sustain life supporting chemical reactions. It dissolves varied products of digestion and transport them to the rest of the body. Similarly, it dissolves diverse metabolic wastes and helps drain them out of the body. Besides, role of water in disturbing the body heat efficiently, thereby regulating body’s temperature is vital water accomplishes this role ideally because it has high thermal conductivity ensuring rapid heat transfer from one part to the other. Drinking a lot of water is an inexpensive way to stay healthy. Even excess of water is harmless. Drinking a litre of water, the first thing that we do in the morning, is kidney-friendly.

What is the vital role of water in human body?