On the day she is to be interviewed for an important new position, Rachel awakens with a severe toothache. During the interview she feels no pain; not until 30 minutes later does she become aware again of the troublesome toothache. Rachel's experience is best explained by:

A) the opponent-process theory.
B) Weber's law.
C) the gate-control theory.
D) the Young-Helmholtz theory.
E) frequency theory