526. Who said this statement? "I flatter myself having discovered the method that nature employs to purify air. It is vegetation."
527. Who suggested that life must have developed from the simple inorganic molecules like methane, hydrogen etc. which were present on the earth soon after it was formed?
528. Why it is not advisable to sleep under a tree at night?
529. Why the white blood corpuscles are popularly called "soldiers of the body”?
530. Why was DDT banned which an organ chlorine compound, used first to control malaria, carried in mosquitoes and later to a variety to insect pests?