Answer:Here are some possible causes and effects of population density in Houston and Yokohama:HoustonCauses:1. Economic Opportunities: Houston is a major hub for the energy industry, particularly oil and gas, attracting workers from across the country and the world.2. Immigration: Houston has a significant immigrant population, with people moving from various countries, contributing to the city’s population growth.3. Urbanization and Development: Continuous urban sprawl and the development of affordable housing and infrastructure have led to increased population density.Effects:1. Traffic Congestion: The high population density contributes to heavy traffic, leading to longer commute times and increased pollution.2. Strain on Public Services: The growing population puts pressure on public services such as healthcare, education, and law enforcement, often leading to challenges in meeting the demand.3. Housing Market Pressure: With increasing demand for housing, home prices and rental costs can rise, making affordable housing less accessible.YokohamaCauses:1. Proximity to Tokyo: As a major port city near Tokyo, Yokohama attracts people for job opportunities, especially in finance, trade, and technology sectors.2. Economic Growth: The city's economic vitality and industries like shipping, manufacturing, and technology drive population growth.3. Limited Land Area: Due to its location and limited available land, Yokohama experiences higher population density as people settle in smaller, urbanized areas.Effects:1. High Cost of Living: Increased population density in Yokohama has resulted in higher living costs, particularly in housing and daily expenses.2. Environmental Strain: The dense population can lead to environmental issues like air and noise pollution, particularly in industrial zones.3. Overcrowded Public Transportation: With high population density, public transportation can become overcrowded, leading to longer wait times and a decrease in quality of life for commuters.Both cities face challenges related to their population density, but they also offer opportunities driven by their economic importance, infrastructure, and cultural significance.