【注音】：qián kǒu 书籍出版术语。前口也称口子或口子边、书口。指书刊的翻阅口，即订口的相对面。
纤毛虫最重要的3个类群为下毛目、肾形目和前口目，其中又以下毛目种类最丰富。
The 3 most important groups of soil ciliates were Hypotrichida, Colpodida and Prostomatida, among which Hypotrichida had the greatest richness of species.
有些候鸟一口气横穿撒哈拉沙漠和地中海，而有些则在穿越前在北非稍作休整。
Some birds traverse the Sahara and the Mediterranean Sea in a one go, while others make a pit-stop in northern Africa before crossing.
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