The correct option is
B Adrenal
A. Testis are the primary male sex organ that secretes testosterone hormone which stimulate spermatogenesis and development of secondary sexual characters in males.
B. Adrenal gland is present on upper side of kidneys and has two parts, adrenal cortex which secrete glucocorticoids, mineralocorticoids and sexocorticoids and adrenal medulla which secrete adrenaline and nor-adrenaline hormone. Adrenaline is secreted in response to stress in the body and is known as emergency hormone. Thus, adrenal gland is an emergency gland.
C. Thymus gland is associated with the development of immune system and present on the dorsal side of heart. It secretes thymosin hormone which plays an important role in the differentiation of T-lymphocytes.
D. Pituitary gland is the master gland that regulates the activity of other endocrine glands and secretes many hormones like growth hormone, follicle stimulating hormone, thyroid stimulating hormone etc.
So, the correct answer is 'Adrenal'.