Respuesta :
C) The author uses comparison and contrast.
The main idea is that cold and allergies may seem similar, but are quite different (as you can see from the topic/first sentence). To help the reader understand this idea, he/she talks about the differences (aka compares/contrasts) the cold and the allergy. He/she is comparing/contrasting between the cold and the allergy when he says "how do you know if you have a cold or allergies?" and then proceeds to answer that question.
The main idea is that cold and allergies may seem similar, but are quite different (as you can see from the topic/first sentence). To help the reader understand this idea, he/she talks about the differences (aka compares/contrasts) the cold and the allergy. He/she is comparing/contrasting between the cold and the allergy when he says "how do you know if you have a cold or allergies?" and then proceeds to answer that question.