Here's a problem to solve: Tobias rode his bike on a road for a 2 hr period. On average, he passed a 1 km marker every 3 min during this period. Which of the following was his average speed for this 2 hr period?

Among the 4 following options, which is the correct answer?

- A: 10 km/hr
 
- B: 15 km/hr
 
- C: 20 km/hr
 
- D: 25 km/hr
 