Explanation : (D) The human ear can respond to minute pressure vibrations in the air if they are in the audible frequency range of approx 20Hz to 20 KHz(20000 Hz)·
Explanation : (B) A computer works when we give an input first. This input is processed by its processor to give output. So the correct sequence is Input → Processing → Output.
Explanation : (D) Clotting of blood occurs due to the presence of platelets in the blood. These are the tiny particles in the blood released into the bone marrow that gather together and form a barrier to further bleeding.
Explanation : (B) A clear cloudless sky appears blue at day time because molecules in the air scatter blue light from sun more than they scatter red light