An Experimental Subject Is Isolated in an Underground Room with No

Multiple Choice

An experimental subject is isolated in an underground room with no windows,no clocks,and no contact with the outside world.Researchers monitoring his behavior observe that he eats breakfast a little bit later each day.What term best describes the subject's biological activity? 

A) Circadian rhythm
B) Free-running rhythm
C) Jet lag
D) Phase shift
E) Entrainment