Although allergic reactions are triggered by allergens like pollen and fungi, the actual cause of the symptoms like mucous production and constricted airways is

Body's immune response.

Explanation:

When body encounters any foreign particles like pollen grain, fungi and some other allergens body evokes immune response.

The primary response of the body is generated by the immune system of the body. There is a increased mucus production and constricted airways so that more pollen grains cannot enter the body.

i believe the correct answer from the choices listed above is the first option. the scientists need to look at the   validity of data, claims, hypotheses, and observations before  developing an argument. they base their arguments on facts that are present and they make sure they have proofs. 

explanation:

it would affect precipitation by causing flooding in some areas of the world due to climate increasing, causing the glaciers in the northern and southern pole of our planet to melt.

i wish you would have provided choices to simplify it and allow me to give an exact answer.