Final answer:
D. Right after the rain has stopped. Roads become most slippery right after the rain has stopped.
Step-by-step explanation:
When roads become very slippery depends on the timing of the rain. Roads become most slippery right after the rain has stopped. During the rain, the water quickly washes away oil and gasoline stains from the road, making it less slippery. However, as the rain starts to subside, the water mixes with the oil and gasoline on the road surface, creating a thin layer of water and oil that makes the road extremely slippery