The systemic circuit:

The systemic circuit sends oxygen-rich blood to the tissues.

It is part of the circulatory system that carries blood away from the heart, delivers it to most of the organs and tissues, and returns it to the heart again.
Choice A is wrong because it describes the pulmonary circuit, which brings oxygen-poor blood from the heart to the lungs.
Choice B is wrong because it is the opposite of what the systemic circuit does.
The systemic circuit brings oxygen-rich blood from the heart to the tissues, not from the tissues.
Choice C is wrong because it is also the opposite of what the systemic circuit does. The systemic circuit sends oxygen-poor blood to the heart, not from the heart.

Hormones that the posterior pituitary secretes are synthesized in the hypothalamus.

They are made by neurons in the hypothalamus and stored and released by the posterior lobe of the pituitary gland, a small organ at the base of the brain.
They regulate water balance, blood pressure, and uterine contraction in the body.
Choice A is wrong because the anterior pituitary synthesizes its own hormones, such as growth hormone, thyroid-stimulating hormone, and prolactin.
Choice C is wrong because the thalamus is not involved in hormone synthesis or secretion. It is a part of the brain that relays sensory and motor signals to the cerebral cortex.
Choice D is wrong because the posterior pituitary does not synthesize hormones. It only stores and releases hormones made by the hypothalamus.