Cities of high population densities develop on plains because I. act as climate barriers II. have fertile soils III. lack heavy rainfall IV. have terrain wi...

The statement that cities of high population densities develop on plains because they have fertile soils and terrain with ease of communication is true, but the statement that plains lack heavy rainfall or act as climate barriers is not always the case. Plains provide favorable conditions for the development of cities due to their flat and open terrain, which allows for easy movement and construction of infrastructure such as roads, railways, and buildings. Additionally, plains often have fertile soils that support agriculture, which can serve as a source of food for the city's population. However, the claim that plains lack heavy rainfall or act as climate barriers is not always true. While some plains may receive less rainfall than other regions, this is not a universal characteristic of all plains. Furthermore, plains do not necessarily act as climate barriers. They can be affected by climatic factors such as temperature, humidity, and wind patterns. Thus, the factors that contribute to the development of cities on plains are primarily fertile soils and ease of communication due to the flat terrain, rather than lack of heavy rainfall or climate barriers. Therefore, the option that best describes the reason why cities of high population densities develop on plains is II and IV only, which are fertile soils and terrain with ease of communication.