84 pts !  and BRAINLIEST TO FIRST CORRECT ANSWER
Marika is training for a track race. She starts by sprinting 100 yards. She gradually increases her distance, adding 4 yards a day for 21 days.  Which explicit formula models this situation?
	A.	an = 21 + (n – 1)4
 		B.	an = 4 + (n – 1)100
 		C.	an = 100 + (n – 1)4
 		D.	an = 100 + (n – 1)21