What is the meaning of the following traffic sign?

- Careful, danger of sliding.
- Correct answer: Traffic congestion ahead (illuminated sign).
- Careful, men at work.
- Caution! Keep distance.
Why this is the answer
The correct answer in the official bank: Traffic congestion ahead (illuminated sign).
The sign warns of traffic congestion further along the road, and it is an illuminated sign. When you see it, slow down, be more alert and be ready for the vehicles ahead of you to stop suddenly. The cars drawn in a row stand for a queue of vehicles, so this is not a keep-distance sign.