
a.

b.

c. "...the KIPP academy in Philadelphia, for instance, gives its students a shirt emblazoned with the slogan “Don’t Eat the Marshmallow.” - John Lehrer, The New Yorker, May 18, 2009 - http://www.newyorker.com/reporting/2009/05/18/090518fa_fact_lehrer?yrail

d.
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I think the test makes sense – my intuition is that this tests whether or not you have the willpower to resist immediate self-gratification for greater benefits in the long term. I’d imagine that that can be a fairly good indicator of success