Final answer:
When using a fire extinguisher, aim the nozzle at d) the base of the flames to cut off the oxygen supply and extinguish the fire effectively.
Step-by-step explanation:
When using a fire extinguisher, it is important to aim the nozzle at the base of the flames. This is because the base of the fire is where the fuel source is located, and by targeting it, you can cut off the oxygen supply and extinguish the fire more effectively.
Using a sweeping motion up and down the height of the flames (option a) or aiming at the middle section (option b or c) may not be as effective in putting out the fire. Directing the extinguisher's stream of water or foam at the base helps to cool the fuel and disrupt the combustion process.