不定项选择题：An introductory sentence for a brief summary of the passage

An introductory sentence for a brief summary of the passage is provided below．Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage．Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage．This question is worth 2 points．
根据以下材料，回答27-28题。