In ________, a cell increases the number of hormone receptors and becomes more sensitive to the hormone.

A) amplification
B) positive feedback
C) down-regulation
D) up-regulation

Up-regulation

The process by which a cell increases the quantity of a cellular component, such as RNA or protein, in response to an external stimulus.

Amplification

In a biological context, the process by which a signal is intensified, as in the enhancement of a signal in a biochemical pathway.