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Load factor--the first answer option is correct--is a standard indicator of utility business efficiency, and historically important for transportation history. Perhaps in class, a historical example included data from Buffalo or Cleveland, but not Pittsburgh, and was presented alongside other considerations of public utility businesses. For students who didn’t pay attention to course content, the wrong answers sound plausible and the question stem doesn’t provide nearly enough for the internet to help.
More Resources for Multiple Choice Questions
Weimer, MaryEllen. "Examining Your Multiple-Choice Questions." Faculty Focus. 26 February 2014. http://www.facultyfocus.com/articles/teaching-professor-blog/examining-multiple-choice-questions/
Center for Teaching and Learning at the University of Texas at Austin. "Multiple Choice Questions." http://ctl.utexas.edu/teaching/assess-learning/question-types/multiple-choice
Teaching Effectiveness Progam at the University of Oregon. "Writing Multiple-Choice Questions that Demand Critical Thinking." http://tep.uoregon.edu/resources/assessment/multiplechoicequestions/mc4critthink.html