Answer:
A. Technician A only.B.
Explanation: The fuel system of a vehicle is made up of the fuel pump,the fuel filter,the injector or carburettor and the fuel tank. The main function of the fuel system is supply fuel to the engine of a vehicle. In order to check for leakage in the fuel system a small pressure smoke is usually installed in the fuel system.
Nitrogen at low pressure has also been used to check for leakage in the fuel system of a vehicle.
To solve this problem we will apply the concepts related to wave velocity as a function of the tension and linear mass density. This is

Here
v = Wave speed
T = Tension
= Linear mass density
From this proportion we can realize that the speed of the wave is directly proportional to the square of the tension

Therefore, if there is an increase in tension of 4, the velocity will increase the square root of that proportion
The factor that the wave speed change is 2.
The answer is going to be B