Final answer:
A zero reading on an air restriction dash gauge could be caused by a bad restriction gauge, a plugged air filter, or a torn air filter, but not an opening in the intake system.
Step-by-step explanation:
A zero reading on an air restriction dash gauge could be caused by any of these EXCEPT: (A) a bad restriction gauge. (B) a plugged air filter. (C) an opening in the intake system. (D) a torn air filter.
A bad restriction gauge, a plugged air filter, and a torn air filter can all lead to a zero reading on an air restriction dash gauge. However, an opening in the intake system would not cause a zero reading.
For example, if there is a hole in the intake system, air can bypass the air filter and enter the engine without being restricted. As a result, the air restriction dash gauge would not detect any restriction and would show a reading above zero.