Gina Comes Home to a Sink Full of Dirty Dishes

Gina comes home to a sink full of dirty dishes and remarks, "Yuck, what a horrible smell!" She then peels an orange and sighs, "Oh! That smells much better!" What allows Gina to distinguish between the different smells?

A) Na⁺ channels are activated for pleasant smells; Cl⁻ channels for unpleasant smells.
B) The process of sensory adaptation differs from smell to smell.
C) The amplitude of an action potential is higher for pleasant smells.
D) The combination of activated receptors differs from smell to smell.
E) Unpleasant smells activate more receptors than pleasant smells.