It's "because".
They phrased their request in three different ways [to cut in line]:
“May I use the Xerox machine?” “May I use the Xerox machine because I have to make copies?” “May I use the Xerox machine because I’m in a rush?”
Both requests using “because” made the people already making copies more than 50% more likely to comply, researchers found.
Who tf calls it a Xerox anymore?