One manufacturer boxes screws so that each box weighs the same no matter what size the screws are. The graph shows the amount of allowed weight remaining in a given shipment depending on the number of boxes of screws already included.

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.