Explanation:

- Car A leaves at 8:30 a.m. traveling at 40 km/h.

- By the time Car B leaves at 9 a.m., Car A has already been traveling for 0.5 hours.

- Car A covers 20 km in this time (40 km/h x 0.5 hours).

- Car B starts at 9 a.m. at 50 km/h.

- To catch up with Car A, we need to calculate when the distance covered by Car B equals Car A plus the 20 km head start.

- Both cars meet when Car B has traveled the distance Car A + 20 km.

- Time taken by Car B to catch up:

- Relative speed: 50 km/h - 40 km/h = 10 km/h

- Distance to cover: 20 km

- Time = Distance ÷ Relative Speed = 20 km ÷ 10 km/h = 2 hours

- Car B's distance in 2 hours:

- Distance = Speed x Time = 50 km/h x 2 hours = 100 km

- Correct Option:

- Option 2, 100 km, is the correct choice.