Assertion . Mast cells in human body release excessive amount of inflammatory chemicals which cause allergic reactions.
Reason . Allergens in the environment on reaching human body stimulates mast cells in certain individuals

Answer

A

Explanation

The symptoms of an allergic reactio develop in response to histamine. Mast cells release a large amount of histamine into the blood stream and it also as initiator of the inflammatory response.
The aids the arrival of leucocytes at a site of intection . Histamine stimulates capillary dilation, increased capillary permeability, clousre of bronchial tubes, mucus secresion, pain and swelling.