Final answer:
Osmoreceptors are located within the 5) anteroventral tip of the third ventricle. Hence, option 5) is correct.
Step-by-step explanation:
Osmoreceptors are located within the anteroventral tip of the third ventricle. Osmoreceptors are specialized cells that detect changes in osmotic pressure or concentration of solutes in the blood.
In the brain, they are mainly found in the hypothalamus, specifically in the anteroventral tip of the third ventricle.