What is meant by anterior and posterior region in our body?

"Anterior" means 'nearer to the front'.  The anterior region of the body
is the region that includes the parts that are nearer to the front, like
toes and eyes.

"Posterior" means 'further back in position'.  The posterior region of the
body is the region that includes the parts whose position is further back,
like buttocks and heels.

- 24 carbon atoms, 48 hydrogen atoms, and 24 oxygen atoms

Explanation:

Glucose is a simple carbohydrate and a compound that is made of the elements carbon, hydrogen, and oxygen.

One molecule of glucose contains six carbon atoms, 12 hydrogen atoms, and six oxygen atoms.

Therefore, four molecules of glucose will have 24 carbon atoms, 48 hydrogen atoms, and 24 oxygen atoms.

That is; 4(C₆H₁₂O₆), thus, C = 4×6 =24, H = 4×12 =48, and O = 4×6 =24.