Final answer:
The leading causes of death in the year 1900 were infectious diseases, such as tuberculosis and pneumonia or influenza. Infectious diseases were more common in developing countries, while non-communicable diseases, such as heart disease and cancer, were more prevalent in developed countries.
Step-by-step explanation:
The leading causes of death in the year 1900 were b) Infectious diseases, tuberculosis and pneumonia or influenza.
Infectious diseases were more prevalent in developing countries, while non-communicable diseases, such as heart disease and cancer, were more common in developed countries.
With the advancement in medical research and the availability of antibiotics, the impact of infectious diseases has decreased in developed countries.