How many water molecules are created when 32 grams of oxygen react completely with 4.0 grams of hydrogen?
a. 2
b. 20
c. 6.02 × 1023
d. 1.2 × 1024

Although respiratory organs vary across different organisms, they all contain respiratory surfaces that have a large surface area and are extremely thin. explain why having an extremely thin respiratory surface with a large surface area is advantageous for the process of gas exchange