Final answer:
To communicate a left turn while driving, use the left turn hand signal by extending your left arm straight out from the window or left side of the vehicle.
Step-by-step explanation:
To communicate that you're turning left while driving, you must use the left turn hand signal. This hand signal involves extending your left arm straight out from the window or left side of the vehicle. This is an important signal for other drivers to know your intention and to ensure safe navigation on the road.