论述往复式压缩机级间压力超过正常压力的原因及排除故障的方法。
Which statement is true regarding Flashback Version Query？ （） It returns versions of rows only within a transaction.。 It can be used in subqueries contained only in a SELECT statement.。 It will return an error if the undo retention time is less than the lower bound time or SCN specified.。 It retrieves all versions including the deleted as well as subsequently reinserted versions of the rows.。
应用成本法评估机器设备，如何估算经济性贬值？
You create a data block based on a relational table containing a REF column. You select the REF column for your form module. What is true about the items based on the REF column attributes?（） The Query Only property is set to Yes. 。 The Conceal Data property is set to Yes. 。 The Insert Allowed property is set to Yes. 。 The Update Allowed property is set to Yes.。
垂直接地体宜采用长度不小于（）m（特殊情况下可根据埋设地网的土质及地理情况决定垂直接地体的长度）的热镀锌钢材，垂直接地体间距为垂直接地体长度的1~2倍，具体数量可以根据地网大小、地理环境情况来确定，地网四角的连接处应埋设垂直接地体。 1.5。 2.0。 2.5。 3.0。
关于家庭暴力的预防下列说法不正确的是（）。
