What occurs when disease affects a greater number of people than is usual for the locality or the spreads to areas not usually associated with disease

Then we are dealing with a pandemic and should trigger a coordinated response of local and central authorities.  If a disease and cases are limited to one region in a country and are a common event, then it is said that´s an endemic illness.  But when there are registered outbreaks of that desease in new areas and it spreads to many other regions or even other coutries, we call it a pandemic. The best example is today´s coronavirus pandemic that is affecting the whole world.

Explanation:

b.

developed countries have tended to improve the environment, while developing countries have tended to damage it.