Artificial light, extended work-time and reduced sleep-time disrupt the activity of

The pineal gland secretes which hormones?
$I. Serotonin$ $II. ACTH$ $III. MSH$ $IV. PRL$ $V. Melatonin$ $VI. FSH$
The correct option is:

Identify the correct gland on the basis of the following characteristics:
$(I)$ It is located on the dorsal side of the forebrain.
$(II)$ It plays a very important role in the regulation of the $24$-hour rhythm of our body.
$(III)$ It helps in maintaining body temperature.
$(IV)$ Its hormone influences metabolism as well as defense capability.

From which one of the following,the melatonin is derived?

Suggest a suitable word for the fourth place: Darkening of skin : $MSH$ :: Lightening of skin : .......

George comes on a vacation to India from the $U.S.$ The long journey disturbs his biological system and he suffers from jet lag. What is the cause of his discomfort?