Melatonin is secreted by the Pineal body, also known as the pineal gland. Melatonin is a hormone that plays a crucial role in regulating the sleep-wake cycle and circadian rhythms. It is produced in response to darkness and helps signal the body that it is time to sleep.
So, the correct option is (A): Pineal body
The current passing through the battery in the given circuit, is: 
A constant voltage of 50 V is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is :
The chemical coordination and integration of all physiological functions in the animal body are jointly synchronized by the neural and endocrine systems. The control and coordination of body functions are executed by the endocrine glands. They are ductless glands that secrete severel hormones to control and coordinate body functions.
The human body has several endocrine glands located in different parts. They cover the pituitary gland, thymus, thyroid gland, pineal gland, parathyroid, pancreas (dual gland), adrenal gland, and gonads (testes and ovaries). The liver, kidney, heart, and gastrointestinal tract also produce hormones in small traces to harmonize the functioning of these organs.
The Hypothalamus comprises groups of secretory cells called nuclei which secrets various hormones. These hormones released by the hypothalamus are important in regulating the synthesis and secretion of pituitary hormones.