Answer:
Both technicians A and B are correct.
Step-by-step explanation:
Variable valve timing is the process of changing the time of a valve lift in the internal combustion engine. This process is usually used to enhance the performance,emissions or the efficient consumption of fuel.
Now a days, variable valve timing is commonly used with a combination of variable valve lift systems in internal combustion engines.
Therefore, technician A(changing the exhaust valve timing how to reduce exhaust emissions) and technician B (it changes in the intake valve timing helped increase low speed torque) are correct.