Respuesta :

Answer:

wars

Explanation:

in the 1900s most of wars happend like world wars,cold war etc

Answer: bacteria or viruses.

In the 1900s, the leading causes of death were due to bacteria or viruses.

Explanation:

It might be said that infectious diseases lead cause of death in the world and in the US. It was after 1950´s that infectious diseases and death rates form these illnesses were reduced.