How does Avogadro's number relate to the concept of a mole?

• A. Avogadro's number is the number of particles in one mole of a substance.
• B. Avogadro's number is the number of atoms in one gram of a substance.
• C. Avogadro's number is the number of liters in one mole of a substance.
• D. Avogadro's number is the number of grams in one mole of a substance.

Answer: (A)