Which gas is most abundant in the Earth's atmosphere?

Which part of the human eye controls the amount of light entering it?

Which blood component is primarily responsible for clotting?

Which vitamin is primarily synthesized in human skin upon sunlight exposure?

Which organ in the human body is primarily responsible for filtering blood and removing waste?

Which gas do plants primarily absorb during photosynthesis?

What is the normal body temperature of a healthy human in degrees Fahrenheit?

Which simple machine is used in a pair of scissors?

Which type of mirror is commonly used in vehicle side mirrors to provide a wider field of view?

Which property of light explains why a straw appears bent when placed in a glass of water?

Which gas is commonly used to fill balloons so that they float in air?