Final answer:
Both technicians provide valid reasons for the blue-gray smoke coming from a car’s exhaust: stuck piston rings or a plugged oil drain passage.
Step-by-step explanation:
The question concerns the diagnosis of issues in automotive technology, particularly the reasons for blue-gray smoke emitted from a vehicle's exhaust. Tech A suggests that the issue may be due to stuck piston rings, which can cause oil to enter the combustion chamber and burn along with the fuel, resulting in blue-gray smoke.
On the other hand, Tech B attributes the potential cause to a plugged oil drain passage in the cylinder head, which can also lead to oil leakage into the combustion area and produce the same blue-gray exhaust smoke. Both technicians are providing plausible reasons for this symptom in an engine. Therefore, the correct answer is Both Tech A and Tech B are correct.