The ground is all wet. It _________ last night.
A．can’t have rained
B．may have rained
C．can have rained
D．must have rained
答案：D
考查情态动词表推测。时间是last night，所以要用情态动词加完成时态表对过去事实的推测。can’t have rained表不可能下雨，和前一句矛盾，排除A；may have rained可能下雨了，把握性不大，和前一句不符，排除B；can不能用于肯定句表推测，排除C；所以选D，must have rained肯定下雨了，把握性很大，符合句意。
请认真阅读下列短文,并根据所读内容在文章后表格中填入最恰当的单词。注意：每空一词。 Prepackaged, mass-produced snack foods are hugely popular in grocery stores around the world. Many people are accustomed to choosing snack foods in grocery stores. The first problem with packaged snack foods like cookies, crackers, and other bite-sized options is that they are often loaded with unhealthy materials. The reason for this is fairly easy to understand. Mass-produced foods need to be uniform in color, taste and so on. In order to achieve this uniformity, snack food producers use sugar, salt, and other chemical preservatives (防腐剂) and coloring materials in large amounts. These materials contribute to a rather unhealthy food. In addition to requiring uniformity of taste and appearance, mass-produced snack foods like potato chips and candies need to be shelf stable. Preservatives and complex packaging make products shelf stable, but this stability and non-perish ability (抗腐性) often come at the expense of nutrition. One reason that pre-made snacks are so popular in grocery stores is their prices. Food producers can keep costs down by using established production facilities and processes to quickly produce a huge amount of food. Shoppers are drawn to what they see at low prices. People who are interested in improving the quality of their snacking can use magazines, books, and the Internet to discover a lot of healthy snacking tips and ideas. Even television shows about health and food sometimes talk about healthy snacking alternatives. Some healthy snacks, like fresh fruit, require no preparation at all. Once people are aware of the drawbacks of clearly cheap and easy snack foods, they can start turning to better options. Soon, perhaps, the old and unhealthy snack options will no longer be profitable for food producers.
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