下列关于梁中钢筋保护层厚度的说法，正确的是（）。 主筋表面至梁表面的距离。 主筋形心至梁表面的距离。 箍筋表面至梁表面的距离。 箍筋形心至梁表面的距离。
When a staging server is used as an environment for testing new data in a default WebSphere Commerce installation， which of the following are true about the staging server？（） The database has a subset of the tables in the production server database.。 The database has a copy of selected data from the production database。 The database logs changes for later propagation.。 The database is accessed as read-only to prevent data corruption.。 The database includes all user and order data for offline processing.。
生态系统中的信息流
如何评价南京国民政府的改订新约运动？
Given: Which code, inserted at line 14, allows the Sprite class to compile?（） Direction d = NORTH;。 Nav.Direction d = NORTH;。 Direction d = Direction.NORTH;。 Nav.Direction d = Nav.Direction.NORTH。
注入催化裂化反应器安全阀防焦蒸汽、再生器的稀相注汽、减压炉和焦化加热的炉管注汽、催化裂化提升管预提升蒸汽的目的是（）。
