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.

• A
  Thyroid gland
• B
  Pineal gland
• C
  Thymus
• D
  Adrenal gland