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

Avogadro's number is the number of particles in one mole of a substance.

Avogadro's number is the number of atoms in one gram of a substance.

Avogadro's number is the number of liters in one mole of a substance.

Avogadro's number is the number of grams in one mole of a substance.