The government is investing in:

Flyovers and underpasses
Upgrading existing roads
Pedestrian walkways and cycling infrastructure
All of the above

The correct answer is: d) All of the above.

The government is investing in all of the above. Flyovers and underpasses are being built to ease traffic congestion, existing roads are being upgraded to improve safety and efficiency, and pedestrian walkways and cycling infrastructure are being built to encourage people to walk or cycle instead of driving.

Flyovers and underpasses are being built to ease traffic congestion. When there is a lot of traffic, it can cause delays and make it difficult to get around. Flyovers and underpasses can help to reduce congestion by providing alternative routes for drivers.

Existing roads are being upgraded to improve safety and efficiency. Old roads can be in poor condition, which can make them dangerous to drive on. Upgrading existing roads can help to improve safety by making the roads smoother and less likely to have potholes. It can also help to improve efficiency by making it easier for drivers to get around.

Pedestrian walkways and cycling infrastructure are being built to encourage people to walk or cycle instead of driving. Walking and cycling are healthy and environmentally friendly forms of transportation. Building more pedestrian walkways and cycling infrastructure can make it easier for people to walk or cycle, which can help to reduce traffic congestion and improve air quality.