The correct answer is: Only assumption I is implicit.
The statement says that the city bus transport corporation has decided to change routes of three buses plying between points A and B in the city to make them economically viable. This means that the buses are not currently economically viable, and the corporation is hoping that the new routes will make them more profitable.
Assumption I is that the buses may get more passengers on the revised routes. This is a reasonable assumption, as the new routes may be more convenient for some passengers.
Assumption II is that many people residing on the old routes may not avail bus services. This is not a necessary assumption. The corporation may have decided to change the routes for other reasons, such as to improve traffic flow or to make the buses more accessible to people with disabilities.
Therefore, only assumption I is implicit.