Which scientific instrument is used to measure very small distances such as the diameter of a wire or thickness of a sheet?

Which structure in the heart prevents the backward flow of blood between chambers?

Which colorless and odorless gas is particularly dangerous because it can cause poisoning without detection unless monitored?

Which gas is primarily responsible for causing the bends in deep sea divers who ascend too quickly?

Which type of chemical bond involves the transfer of electrons from one atom to another?

Which organ in the human body acts as a reservoir for blood and helps filter out old or damaged red blood cells?