单项选择题 CDE is working. However, the customized PATH environment has not been implemented. Which of the following procedures should be performed to activate the implementation?（）

单项选择题 The latest version of a licensed product is already installed. Which of the following methods is most appropriate to load an older version of a licensed program product over the latest version?（）

单项选择题 Which of the following statements is TRUE about mounting a file system?（）