Final answer:
Better sanitation and nutrition were outcomes of the Industrial Revolution, which improved public health infrastructure and promoted scientific advances in agriculture, leading to lower death rates and higher life expectancy.
Step-by-step explanation:
Better sanitation and nutrition generally resulted from the Industrial Revolution. This era brought about the invention of the steam engine, which allowed environmental conditions to be manipulated to suit human needs, spurring exponential population growth.
Furthermore, the Industrial Revolution led to scientific and technological advances that resulted in improved water supplies, sewers, and personal hygiene.
Combined with better farming techniques and increased food supply, these factors significantly lowered death rates.
Additionally, the rise in life expectancy was fueled by the development of immunizations and the understanding of the importance of cleanliness and public health measures. As such, the correct answer to the student's question is a. Industrial Revolution.