I think it was meant to read "he received a B.S. degree in physics" but I'm not sure (pg vii)
You can read about the MIT undergraduate degree programs
here. Quoting a relevant passage:
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The program for the SB takes four years of full-time study for most students. Of the freshmen who entered between 1992 and 1996, the percentage of students who received their degrees within six years of entrance was about 90 percent.
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