Which technique does the author use to help readers understand the meaning of contaminants in paragraph 4?

contaminants definition below

Explanation:

a polluting or poisonous substance that makes something impure.

the cost of attendance or coa is an approximate budget for the cost of attendance of the whole academic year. in order to calculate this, universities take into consideration many factors like room and board, tuitions and fees, books, transportation and personal expenses such as medicine, laundry, clothing. all these factors combined make up the final sum to the cost of attendance in each university.

i’m alive so yes and the author is a technique idiom