Critical Reasoning (CR) | For years the beautiful Renaissance buildings in Palitito have been da

For option (C), how can we deduce that if 1/4 of the time is taken in transporting passengers from one site to another, the remaining 3/4 of the time can only be taken in either parking or idling?
Some other scenarios that can happen:
1. Time spent driving around without any passengers
2. Time spent driving to another place to park the bus before he/she completes his duty

The reason why I eliminated this option is that it seemed to take an assumption that the remaining time can only be spent in either parking oridling. ­