An athlete trains by running 4 km in 20 minutes without stopping. For 30 seconds in each minute the athlete increases the intensity significantly before returning to the normal intensity.
Which row in the table indicates the type of training and the method that is being used?
| Type of training | Training method | |
| A. | Aerobic | Fartlek |
| B. | Anaerobic | Fartlek |
| C. | Aerobic | Interval |
| D. | Anaerobic | Interval |