Which type of stimulus is an allergen, such as pollen?

a. response to a stimulus

b. external stimulus

c. internal stimulus

d. inborn stimulus

I think the correct answer from the choices listed above is option B. External stimulus is the  type of stimulus an allergen, such as pollen, is classified. This is because this allergen is obtained outside the body. So it must be external. Hope this answers the question. Have a nice day.

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The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .