In this question, we are given a velocity-time graph of a moving car on a road and we need to identify the segment that represents the retardation.

Option 1 (AB): This segment shows a positive slope, indicating an increasing velocity. Therefore, this segment does not represent retardation.

Option 2 (BC): This segment shows a negative slope, indicating a decreasing velocity. When the slope of a velocity-time graph is negative, it represents retardation or deceleration. So, this segment represents retardation.

Option 3 (CD): This segment shows a horizontal line, indicating a constant velocity. Retardation is characterized by a decreasing velocity, so this segment does not represent retardation.

Option 4 (None): This option suggests that none of the segments represent retardation, but since option 2 (BC) represents retardation, this is not the correct answer.

Therefore, the correct answer is option 2 (BC) since it represents the segment of the graph that represents retardation.