Which sentence best describes the relationship between the mole and avogadro’s number?

Avogadro's number represents the number of individual molecules that are present in a mole of material. This number is 6.02*10^23 regardless of the element or substance you are dealing with. 

A good sentence would be something like, "A mole of a certain material will contain 6.02*10^23 molecules, which is known as Avogadro's number."

Hope this helps