Which of these are symptoms of an allergic reaction?

Although the reasons why allergies develop aren’t known, there are some substances that commonly cause an allergic reaction. People who have allergies are typically allergic to one or more of the following:

Explanation:

Doctors don’t know why some people experience allergies. Allergies appear to run in families and can be inherited. If you have a close family member who has allergies, you’re at greater risk for developing allergies.

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Hint The  Brainliest :)

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

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