Explanation:

• Dexamethasone, a corticosteroid, is similar to a natural hormone produced by adrenal glands. It relieves inflammation (swelling, heat, redness, and pain) and is used to treat certain forms of arthritis; skin, blood, kidney, eye, thyroid, and intestinal disorders (e.g., colitis); severe allergies; and asthma.
• WHO has been administering the use of Dexamethasone drug for recovery trials in severe patients of Covid-19. So, that it immune response of the body when confronted by a viral infection such as Covid-19. 
• The Multi-system Inflammatory State is a rare illness that causes inflammation of the blood vessels leading to low blood pressure.It affects the entire body as it causes a build-up of fluid in the lungs and other organs. Hence all statements are correct.