题目内容
下列化合物中含有（双重致活的）活泼亚甲基的是
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丙二酸二乙酯可用于合成
所有二元酸酯均可以发生分子内酯缩合反应形成环状化合物。
含有活泼亚甲基化合物通常作为迈克尔供体参与“迈克尔（Michael）”加成反应。
判断时态Analyze the following sentences to see what tenses they belong to.P表示一般过去时态，PP表示现在完成时态1) I've only been here for ten minutes or so.2) Ted has always worked in an accounting department.3) Mark has worked for this large company for many years.4) John graduated from Florida State University in 1990.5) We had the same weather in Detroit last year.6) He has never made a serious mistake at work.7) What has the weather been like recently?8) Robert went to school part-time while he worked full time.9) Robert has received two promotions so far.10) Robert has decided to look for a job in a larger company.
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