Answer:
When the red test lead is positive (+) and the black test lead negative (-), the meter will register voltage in the normal direction.
Explanation
Answer: The new pressure is 3 psi.
Explanation:
Given:
= 12 psi, 
= ?, 
Formula used is as follows.

Thus, we can conclude that the new pressure is 3 psi.
C is correct. Have a good day!