The answer is HIV. Hiv or human immunodeficiency is a virus that can weaken the body's immune system. Infection with HIV causes a life-threatening illness called AIDS also as immunodeficiency syndrome.
Oxygen in the air can cause sliced fruit to brown, a process called enzymic browning (an oxidation reaction). Phenols and the enzyme phenolase are found in the cells of the apple, and when these are exposed to oxygen in the air, for example through slicing, the oxygen causes a reaction.
2,3,4, are right 1 is incorrect as far as I can tell
