Correct Option: B

Mast cells are granulated leucocyte cells. Their granules contain histamine which is a vasodilator and heparin (an anticoagulant). These take part in body defence and allergic reaction. Vasopressin is released by posterior lobe of pituitary. Relaxin is released by placenta. Calcitonin is released by thyroid. Serotonin and melanin are released by intermediate lobe of pituitary gland.