Technician a says that the burning of the air-and-fuel mixture in the cylinder is called fuel activation. technician b says that the basic function of the upper-end components is to control the flow of air-and-fuel mixture into the engine and the flow of the exhaust gases out of the engine after combustion. who is right?

Both of the Technicians are correct. 

Fuel activation in the cylinder needs air and fuel mixture which Technician A states.  Also, Technician B explained that the upper-end component function is to regulate the air-and-fuel mixture together with the flow of exhaust gases that comes out after combustion. Each of them explained some engine parts which are connected and make a vehicle run.