Why do you believe knowing how elements and compounds react together is essential in everyday matters?

Scientist believe that about 25 of the known elements are essential to life. Just four of these - Carbon (C), Oxygen (O), Hydrogen (H), and Nitrogen (N), - make up about 96% of the human body.

These four elements are found in the basic structure of all biochemical molecules. For example, Glucose is a carbohydrate and it's molecular formula is C6H12O6 - each molecule of glucose is made up of 6 Carbon atoms, 12 Hydrogen atoms and 6 oxygen atoms.

The other elements found can be divided into two main groups - major elements and trace elements.

The human body functions as a result of a large number of the chemical reactions involving compounds of a of these elements.

i'm pretty sure its b i might be wrong though!

there are two significant figures.