The correct interpretation of the y-intercept (0, 31.06) in this context is:
When Michael started training, he was running 5 kilometers in approximately 31 minutes.
The y-intercept represents the predicted time for running 5 kilometers (in minutes) at week 0 (before training starts). The other options do not correctly interpret the meaning of the y-intercept in the context of Michael's 5-kilometer training.