ASVAB Armed Services Vocational Aptitude Battery (#70)

Section: Paragraph comprehension

Some pollutants that render air unsafe to breathe cannot be seen or smelted. Nitric oxide, carbon monoxide, and radon gas are examples. Other pollutants, such as formaldehyde, can be smelted at high levels only but are still unsafe to breathe even at lower levels. You can conclude from the paragraph that formaldehyde

is safer to breathe than nitric oxide.
can never be seen or smelted.
cannot be smelted at lower levels.
is not one of the pollutants that renders air unsafe to breathe.