The correct hand signal to indicate a left turn is:

To indicate a left turn, the correct hand signal is to extend your hand and arm outward. This signal is universally recognized for left turns and helps communicate your intentions to other drivers and pedestrians, especially when your vehicle's turn signals might not be visible. The outward position of your arm clearly shows that you are planning to turn left, allowing others to anticipate your movements and respond appropriately.

In contrast, raising your hand and arm upward is typically used to signal a right turn, while an arm extended downward suggests that you are stopping or slowing down. Not using any hand signal is not advisable, since it can lead to confusion on the road and increase the risk of an accident. Proper signaling is a crucial part of safe driving and helps maintain clear communication on the road.