Answer:
The best answer is "B"
Both Technician A and B
Step-by-step explanation:
The master cylinder is a hydraulic pump. As you pump the pedal, it forces the brake fluid into the calipers/wheel cylinders. However, air compresses quite easily, as such the hydraulic pressure reduce the by large amounts because of the presence of air in the braking system.
The two Technicians are both right.