单选题：根据下面资料，回答题 At dawn one morning in early May, Sean Cosgrove i

根据下面资料，回答题
At dawn one morning in early May, Sean Cosgrove is stashing piles of maps, notes and photocopied documentsin his gym bag before heading for West Milford High, a rural school in northernmost New Jersey. On his 30-minutecommute, the young former investment banker tries to dream up new ways of lifting the monumentally forgettable
Mexican War off the textbook page and into his students' imaginations. Can he invoke the storied memories of Rob-ert E. Lee, who cut his first military exploits on the plains of Veracuz--or will he be met with thundering responsesof "Who's Lee"? Should he raise James K. Polk out of the mystic chords of memory, and hope, for a nanosecond,
that the kids will care about the first U. S. president who stepped aside because he'd accomplished everything hewanted? Let's think some more. Well, there's always the Alamo. And hey, isn't that the teachers' parking lot up a-head?
It's never an easy task. These big kids in big jeans and ball caps, come to his history classes believing that his-tory is about as useful as Latin. Most are either unaware or unimpressed that the area's iron forges once produced ar-tillery cannon for George Washington's army. Their sense of history orbits more narrowly around last month's adven-tures on "Shop Rite Strip", the students' nickname for downtown West Milford, once a factory town, now a Mag-net for middle-class vacationers.
Cosgrove looks uncommonly glum as he thumbs through a stack of exams in the teachers' lounge. "I can't be-lieve anyone in my class could think John Brown was the governor of Massachusetts, "moans Cosgrove,28, point-ing to one student's test paper. He had to be sleeping for days on end. The same morning~ students in his college
bound class conld name only one U. S. Supreme Court justice--Clarence Thomas. All his wit, energy and beyond-the-textbook research can't completely reverse the students' poor preparation in history, their lack of general knowl-edge, their numbness to the outside world. It's the bane of history teachers at every level. When University of Ver-mont professor James Loewen asked his senior social-science majors who fought in the Vietnam War,22 percent an-swered North and South Korea. Don't these kids even go to the movies?
What did Cosgrove do before he became a teacher teaching history? A．A clerk working in a gym.
B．A man running a bank.
C．A sportsman.
D．A historian.