Question

air quality is a major issue in the laerdal tunnel. what is the main problem?
a the tunnel can quickly fill with dangerous gases given off by cars.
b unhealthy mold spores get trapped in the air vents.
c air that is too cold makes car engines work harder.
d dust from the dry mountain rock walls makes the air smell bad.

Explanation:

The Laerdal Tunnel is a long road tunnel, so the primary air quality concern stems from vehicle emissions. Cars produce dangerous exhaust gases (like carbon monoxide, nitrogen oxides) that can accumulate rapidly in the enclosed, poorly ventilated space of a long tunnel, creating a severe health and safety risk. The other options are not the main air quality issue for this type of tunnel.

Answer:

A. The tunnel can quickly fill with dangerous gases given off by cars.