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　　● 题目：

　　On 13 July 1907, Baekeland took out his famous patent describing this preparation, the essential features of which are still in use today. (剑5, Test 2 passage 1)

　　● 分析：

　　本句的主句为“Baekeland took out his famous patent”, “On 13 July 1907”为时间状语;“describing this preparation”为现在分词短语做定语，做his famous patent的定语;“the essential features of which are still in use today”为同位语，做this preparation的同位语;而其中“of which are still in use today”为定语从句，做features的定语，关系词为which。