People have a tendency to judge stimuli relative to those previously experienced. for example, if a man's current income level increases, he feels an initial surge of pleasure. however, as he adapts to that income level, he comes to consider it normal. he then requires something better to feel another surge of happiness. this is known as:
a. relative deprivation.
b. the adaptation-level phenomenon.
c. the feel-good, do-good phenomenon.
d. subjective well-being.