Simone Flew from Edmonton, Alberta, to London, Two Days Ago

Simone flew from Edmonton, Alberta, to London, two days ago. Since then, she has been feeling sleepy during the day but has had difficulty sleeping during the night. The probable reason for her difficulty is that

A) airline travel has temporarily disrupted her hypothalamus.
B) she is exhausted from sight-seeing.
C) her body clock is not synchronized with clock time
D) she lost a night's sleep on her flight.