One's motivations and emotions are controlled by the forebrain.
Thus,
among the four choices above, the answer is none other than a. forebrain
Forebrain is the anterior part of the brain. There is what we call the hypothalamus that also controls emotions. Love has to be credited to this part.
For example:
"I love you with all my heart."
The heart does not feel emotions, the hypothalamus does. So instead of heart we replace it with,
"I love you with all my hypothalamus"
