D.

The ovary is the primary female sex organ that produces the female gamete (ovum) and several steroid hormones (ovarian hormones). The two steroid hormones produced by ovary are oestrogen and progesterone. Oestrogens produced by ovary are oestrogen and progesterone. Oestrogens produce wide-ranging actions such as stimulation of growth and activities of females secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters (e.g., high pitch of voice, etc.) mammary gland development oestrogens also regulate female sexual behaviour. 
Alpha cells of islets of Langerhans of the endocrine pancreas secrete a hormone called glucagon. It is a peptide hormone and plays an important role in maintaining the normal blood glucose levels. It acts mainly on the liver cells (hepatocytes) and stimulates glycogenolysis resulting in an increased blood sugar (hyperglycemia). In addition, this hormone stimulates the process of gluconeogenesis which reduces the cellular glucose uptake and utilisation. Thus, glucagon is a hyperglycemic hormone.
The pars distalis region of pituitary commonly called produced anterior pituitary, Growth Hormone (GH), prolactin (PRL), Thyroid-stimulating Hormone (TSH) Adrenocorticotrophic Hormone (ACTH), Luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Over secretion of GH stimulates the abnormal growth of the body leading to gigantism and low secretion of GH results in stunted growth resulting in pituitary dwarfism.

A.

A - receptor, B - synaptic cleft, C - synaptic vesicles and D - Ca²⁺

B.

vestibular apparatus 

Vestibular apparatus of membranous labyrinth is an intricate series of inter-connected and fluid-filled canals which regulates balance and spatial orientation in the absence of vision, the movement of body will be regulated only by vestibular apparatus.
The otolith organs (utricle and saccule) regulates linear acceleration and semicircular canals sense rotational acceleration in various directions.
The cochlea, tectorial membrane and organ of Corti are responsible for transduction of sound waves.

A.

submicroscopic molecular level

Biological organisation starts with submicroscopic molecular level, where four types of molecules, i.e. carbohydrates, lipids, proteins and nucleic acid are organised into organelles of cell.

A.

olfactory epithelium

Bowman's glands (olfactory glands) occur below the olfactory epithelia. Their ducts open on the olfactory epithelial surface. These glands secrete watery mucus to protect and keep the epithelium moist.