[QA] It can be inferred from the first paragraph that ___________.

Question:

It can be inferred from the first paragraph that ___________.

• A.
  water vapor is an air pollutant in localized areas
• B.
  most air pollutants today can be seen or smelled
• C.
  the definition of air pollution will continue to change
• D.
  a substance becomes an air pollutant only in cities