Final answer:
The b) cisterna ambiens contains the pineal gland, which is an endocrine organ located inferior and posterior to the thalamus in the diencephalon, responsible for melatonin production.
Step-by-step explanation:
The pineal gland is an endocrine structure located in the diencephalon region of the brain and is situated inferior and posterior to the thalamus. The structure containing the pineal gland from the options provided is the cisterna ambiens (option b), which is an area of subarachnoid space lying between the midbrain and the cerebrum and covering the pineal gland. This gland is responsible for producing and secreting the hormone melatonin, which regulates sleep patterns and adapts to light-dark cycles, such as in cases of jet lag. Structures such as the thalamus, hypothalamus, and retina arise from the diencephalon during embryological development, but the pineal gland is particularly noteworthy for its role in secreting melatonin based on visual information received from the suprachiasmatic nucleus of the hypothalamus.