Question

morgan knew that toxic smoke rises during a fire, so his safety hood had a long tube reaching to the floor. wearing morgans hood, a firefighter could breathe the cleaner air near the ground.
morgan was roused from home on the night of the tunnel explosion, and he rushed to the disaster site with samples of his safety hood. still in their pajamas, he and his brother frank put on the hoods and bravely entered the tunnel. it was a dangerous test of the invention, but they saved two lives and recovered four bodies before officials closed the site.
morgans safety hood was the model for the gas mask used by the u.s. army during world war i. the gas mask saved countless lives.
how did the safety hood help morgan inside the tunnel filled with poisonous gas?
the safety hood helped morgan keep from getting burned by the poisonous gas.
the safety hood helped morgan breathe the cleaner air near the bottom of the tunnel.
the safety hood helped morgan rush to the site of the explosion in the tunnel.

Explanation:

The text states that the safety hood had a long tube reaching to the floor, allowing the wearer to breathe cleaner air near the ground. This directly relates to the second option which mentions breathing cleaner air near the bottom (equivalent to near the ground in the context) of the tunnel. The first option is incorrect as the hood's function is about breathing air, not preventing burns (the gas is poisonous, not something that burns in the sense of fire - related burns here). The third option is wrong because the text does not say the hood helped in rushing (the rushing was Morgan's action after being roused, not due to the hood's function in the tunnel with gas).

Answer:

The safety hood helped Morgan breathe the cleaner air near the bottom of the tunnel.