The correct option is C hypothalamus
The forebrain consists of 3 parts- cerebrum, diencephalon and olfactory lobes. Diencephalon is visible from the inferior side of the brain. Its roof is called epithalamus, floor is called hypothalamus and the walls are called thalami (thalamus).
Epithalamus is fused with pia mater to form anterior choroid plexus (ACP) which produces CSF.
Hypothalamus is highly vascular and regulates behavior essential for survival of species- feeding, fighting, fleeing, mating. It has a hunger centre, satiety centre, thirst centre, osmoregulatory centres.