Final answer:
The demographic transition is a process where a society moves from high to low birth and death rates, often due to industrialization and economic development. It began in Europe and North America and is now observed in the United States, Europe, and many developing nations.
Step-by-step explanation:
The demographic transition describes the process by which a society changes from having high birth and death rates to low birth and death rates. This transition typically occurs as a country develops from a pre-industrial to an industrialized economic system. Historically, industrialization led to improved living conditions, medical advances, and better nutritional standards, which first caused a decline in death rates, allowing more people to reach reproductive age and boosting population growth. Eventually, as societies continue to develop economically and socially, birth rates start to decline. This is influenced by factors such as increased access to education, changes in the labor market, urbanization, and the increased cost of raising children, leading to smaller family sizes. Therefore, the demographic transition is not a singular event but rather a gradual process that unfolds over time, affecting population dynamics significantly. Option B is the most accurate: The demographic transition is happening today in the United States and Europe as a result of continued development, and it has its roots in the past centuries of industrialization. It has also been observed more recently in many developing nations where death rates have dropped due to medical and technological advancements before a corresponding decline in birth rates.