Option 4 is the right answer. Let us look into the meaning of the given words:
facilities-- a place, amenity, or piece of equipment provided for a particular purpose.
consequences-- a result or effect,
differences--a disagreement, quarrel, or dispute.
difficulties--a thing that is hard to accomplish, deal with, or understand.
The given sentence is about plying a huge number of buses on their regular schedules. The complete sentence is--TMT plies nearly 300 buses and is already facing difficulties in managing regular schedules.