Question

to prevent sewer gas from entering the house, drains are protected by

vents

water heaters.

drains

traps

Explanation:

Traps in plumbing systems hold a small amount of water that acts as a barrier, preventing sewer gas from entering the house. Vents are for allowing air into the system to ensure proper drainage, water heaters are for heating water, and drains are the outlets for wastewater.

Answer:

Traps