Explanation: Repository Manager is a tool used for managing Artifactory repositories. Let's go through each option to understand why it is correct or incorrect:

Option A) Creating folder within repository - This option is possible using Repository Manager. You can create new folders within a repository or move existing folders around to organize your artifacts.

Option B) Creating users and assigning roles - This option is possible using Repository Manager. You can create new users and assign roles to them to manage access to your repositories.

Option C) Taking backup of Repository - This option is not possible using Repository Manager. Although you can configure backup settings for your Artifactory instance, the backup itself must be performed using a separate tool outside of Repository Manager.

Option D) Comparing folders - This option is possible using Repository Manager. You can compare any two folders within a repository to see the differences between them and identify any missing or extra artifacts.

Therefore, the correct answer is C) Taking backup of Repository. This option is not possible using Repository Manager.