Which of the following is an example of data cleaning?

Data cleaning involves the process of correcting or removing inaccurate records from a dataset. In this context, removing unnecessary columns is a clear and relevant example of this process. By eliminating columns that do not contain valuable or relevant information, you enhance the dataset’s quality, reduce complexity, and make it easier to analyze.

Other options, while related to data management, do not directly pertain to the act of cleaning data. Creating a backup of the database is crucial for data integrity and recovery but does not alter the dataset itself. Adding new records contributes to the dataset's content but does not address any existing issues within it. Connecting to data in a database is simply establishing a link to access the data rather than modifying or improving the quality of that data. Thus, the act of removing unnecessary columns stands out as a definitive example of data cleaning.