Question

a pipe or channel that is used to carry and distribute air throughout a building as part of an hvac system
a. valve
b. backflow
c. potable water
d. duct
a device that regulates the flow of water through the plumbing system
the undesirable reversal of water flow within a plumbing system

Explanation:

1. For the first definition ("a pipe or channel that is used to carry and distribute air throughout a building as part of an HVAC system"), the term "duct" (option d) matches as ducts are air - carrying channels in HVAC systems.
2. For the second definition ("a device that regulates the flow of water through the plumbing system"), a "valve" (option a) is a device that controls water flow in plumbing.
3. For the third definition ("the undesirable reversal of water flow within a plumbing system"), "backflow" (option b) is the term for reversed water flow in plumbing.

Answer:

1. "a pipe or channel that is used to carry and distribute air throughout a building as part of an HVAC system" - d. duct
2. "a device that regulates the flow of water through the plumbing system" - a. valve
3. "the undesirable reversal of water flow within a plumbing system" - b. backflow