What does a yellow sign with a black arrow curving left signify?

A yellow sign with a black arrow curving left is a cautionary sign that alerts drivers to a sharp left turn ahead. This sign serves to warn motorists that the road will bend significantly, requiring a reduction in speed to navigate the turn safely. It is crucial for drivers to slow down upon seeing this sign to maintain control of their vehicle and avoid any potential accidents.

The other options do not accurately represent the meaning of a sign depicting a curving arrow. The sign does not indicate anything about traffic light changes, road closures, or minimum speed limits. Instead, it focuses solely on the need for caution due to the sharp turn, promoting safe driving practices in potentially hazardous roadway conditions.