The paragraph is followed by an incomplete phrase or sentence which summarizes the main idea of the paragraph. Choose the missing words of the phrase or sentence.

Daylight saving time began in the United States during World War I, primarily to save fuel by reducing the need to use artificial lighting. Although some states and communities observed daylight saving time between the wars, it was not observed nationally again until World War II.
Daylight saving time in the U. S. reduced （） consumption.