下列关于后除极的叙述，哪项是正确的（） ["早后除极的发生与Ca2+<\/sup>内流增多有关","钙拮抗药对迟后除极无效","早后除极发生在4相中","迟后除极可以发生在2相或3相中","早后除极不引起触发活动"]
在PowerPoint中，采用“另存为”命令，不能将文件保存为（）。 ["文本文件（*.txt）","Web页（*.htm）","大纲\/RTF文件（*.rtf）","PowerPoint放映（*.pps）"]
What are three benefits of performing data definition language （DDL） statements against a partitioned table with the UPDATE GLOBAL INDEXES clause？（） ["Global indexes are rebuilt automatically at the end of the DDL operation thereby avoiding problems with the UNUSABLE status. ","You do not have to search for invalid global indexes after the DDL command completes and rebuild them individually. ","Global indexes are maintained during the operation of the DDL command and therefore can be used by any concurrent query. ","Global indexes remain intact and available for use by data manipulation language （DML） statements even for sessions that have not enabled the skipping of unusable indexes."]
五四运动有什么历史特点？
下列描述中，（）不是施工单位施工阶段质量控制的内容。 ["对所进材料进行质量控制","按规定控制计量器具的使用、保管、维修和检验","严格执行工程变更程序，经有关部门批准后方可实施","按要求进行质量知识培训，并应保存培训记录"]
危险废物
