What factors contributed to the significant increase in life expectancy from 1900 to 1974?

The significant increase in life expectancy from 1900 to 1974 can be attributed to multiple interrelated factors, among which sanitation and nutrition stand out as critical contributors.

Improvements in sanitation practices, such as the implementation of modern sewage systems, clean water supply, and proper waste disposal, profoundly reduced the prevalence of waterborne diseases like cholera and typhoid fever. This shift not only decreased morbidity but also enhanced overall public health, leading to longer lifespans.

Nutrition also played a vital role during this period. The availability of a more varied and nutritious diet, coupled with advancements in agricultural practices and food preservation techniques, helped reduce malnutrition and support better growth and immune function in the population. Improved nutrition emerged as a key factor in reducing the susceptibility to various diseases.

While chemotherapy is a significant advancement in medical treatment, particularly for cancer, its influence on the general population's life expectancy during this period is not as pronounced as the broader public health measures associated with sanitation and nutrition.

Thus, both sanitation and nutrition were central to the remarkable increase in life expectancy during this time, highlighting the importance of public health initiatives and advancements in food systems. The correct response encompasses the contributions of these critical factors in shaping health outcomes in the population.