Which sentence from the text BEST summarizes a main idea of the article? A) People have more ways of marking time, and they do it more precisely.
B) All living things must know the time to adjust to the world as it changes.
C) Ancient people spent most of their time outside.
D) Early calendars were based on the Earth's orbit around the Sun.
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The sentence that BEST summarizes the main idea of the article is option D) "Early calendars were based on the Earth's orbit around the Sun." To explain the answer, we need to analyze each sentence and determine which one conveys the main idea of the article. Option A) "People have more ways of marking time, and they do it more precisely." This sentence talks about how people now have more precise ways of measuring time, but it doesn't directly relate to the main topic of the article, which is the history of calendars and how time was marked in the past. Option B) "All living things must know the time to adjust to the world as it changes." While this sentence recognizes the importance of knowing the time for living things, it doesn't address the main idea of the article, which is focused on ancient calendars and how they were developed. Option C) "Ancient people spent most of their time outside." This sentence provides some information about ancient people, but it doesn't specifically relate to the development of calendars or how time was marked in ancient civilizations. Option D) "Early calendars were based on the Earth's orbit around the Sun." This sentence directly addresses the main topic of the article by explaining how early calendars were developed and what they were based on - the Earth's orbit around the Sun. This information is crucial in understanding the evolution of calendars and how time was marked in the past. Therefore, option D) "Early calendars were based on the Earth's orbit around the Sun" is the best summary of the main idea of the article. This sentence highlights the fundamental concept discussed in the text and supports the article's focus on ancient calendars.