Glucagon hormones are secreted by:

Alpha cells of islets of Langerhans.

The correct answer is Option (4) - Alpha cells of islets of Langerhans.

The pituitary is under the direct control of the hypothalamus which stimulates the secretion of trophic hormones that control the activity of other endocrine glands. 

The adrenal gland is divided into two regions which are the adrenal cortex which secretes aldosterone cortisol, cortisone, estrogens, and androgens; the adrenal medulla which secretes epinephrine and norepinephrine which are tyrosine derivatives.

Pancreas is a composite gland  which acts as both exocrine and endocrine gland. The endocrine pancreas consists of ‘Islets of Langerhans’. There are about 1 to 2 million Islets of Langerhans in a normal human pancreas representing only 1 to 2 per cent of the pancreatic tissue. The two main types of cells in the Islet of Langerhans are called α-cells and β-cells. The α-cells secrete a hormone called glucagon, while the β-cells secrete insulin.