Mrs. Daniel packs reams of paper into boxes. The box has a mass of 18
ounces, and each ream of paper weighs 22 ounces. If the function
y = 22x + 18 describes the total mass, the variable x represents the —
A.total mass of a box filled with reams of paper
B.total number of boxes filled with reams of paper
C.mass of each ream of paper inside a box
D.number of reams of paper packed in a box