When programming in an OOP language classes are created to represent real-life objects, people, places etc. from the real world. Programming in the general allows you to cut down your code and making it more efficient by applying the same necessary functions to all of the objects that classify under the same category. For example by programming "in the general" and creating an Animal class you can create all of the functions/behaviors that animals tend to have. Then you can apply these functions/behaviors to various animals such as a Cat, Dog, Horse, etc. But if you program in the specific you cannot apply a Cat class to a Dog since they are not the same thing.
3.In the Remove Duplicates dialog box: If your data has headers, make sure the 'My data has headers' option is checked. Make sure the column is selected (in this case there is only one column).