The correct answer is - hospitals.
The infrastructure of a country is a set of built objects where services are offered, and people work, or are using them in their daily lives for their activities.
From the options provided, the only one that is an actual object, are the hospitals. In the infrastructure of a country also fall the schools, colleges, and universities, roads, airports, administration buildings, factories etc. They all have someone that works in them, something that offer, and are used, to and by the general public, and the more developed the infrastructure is, it usually means that the more developed the country itself is as well.
