Identify the hormone with its correct matching of source and function.
a. Oxytocin - posterior pituitary, growth and maintenance of mammary glands
b. Melatonin - pineal gland, regulates the normal rhythm of sleep wake cycle
c. Progesterone - corpus-luteum, stimulation of growth and activities of female secondary sex organs
d. Atrial natriuretic factor - ventricular wall increases the blood pressure

Hint: Oxytocin is secreted by the posterior pituitary and is called milk ejection hormone and also a birth hormone. Melatonin is released by the pineal gland and it works as a biological clock. Progesterone is released by the corpus luteum and it is called the pregnancy hormone. Atrial natriuretic factor dilates the blood vessels.

Complete answer:
Hormones are the small molecules of low molecular weight and they act as an intercellular messenger.
> Oxytocin- this hormone is released by the posterior pituitary. Oxytocin is also called as milk ejection hormone as it ejects milk from mammary glands during suckling. It is also called birth hormone as it causes labor pain/ uterine contraction for the delivery of the baby.

> Melatonin- this hormone is released by the pineal gland. It works as a biological clock and is involved in the regulation of daily or sleep-wake cycles called a circadian cycle.

> Progesterone- this hormone is released by the corpus luteum. It is called a pregnancy hormone as it governs the changes during pregnancy. It is a type of steroid hormone.

> Atrial natriuretic factor- this hormone dilates the blood vessels and decreases blood pressure. An increase in blood flow to the heart atria stimulates the release of the atrial natriuretic hormone.

Hence, the correct answer is option (B).

Note: Oxytocin is actually synthesized in hypothalamic supra-optic and paraventricular nuclei and then transported to the posterior pituitary through axons.
Melatonin is Also called sleep hormone and it is derived from tryptophan amino acid. It also helps to maintain normal body temperature.
Progesterone also causes the final preparation of the endometrium for the implantation of the zygote.