Segregation; the two different races are being segregated (separated) from each other. Hope this helps :)
It depends but mostly river is bigger than the lake
The strategy that will help you revise your choice of words to achieve your purpose is to think of what message you want to give such as in an introduction to a topic whereby you want to cover the main points to be expounded on in the main paper or essay or chapter of a book you may be writing to set the stage for their full explanation.
