Read these sentences from a concluding paragraph. Which statement best describes the purpose of sentence 1? 1 By around 1700 BCE, most of the cities along the Indus River had been abandoned 2 The Indian monsoon rains had weakened, causing less extensive floods, and as a result less food was grown. 3. The reduced water supply caused the Indus River valley's population to move eastward toward the Ganges River valley It develops the topic. It restates the essay's thesis statement It reviews evidence presented to readers. It summarizes the main ideas of the essay.