The correct answer is: D. all of the mentioned
Dropbox, Skype, and Google Drive are all file transfer utilities that create a shared folder metaphor using a Web service.
Dropbox is a file hosting service that offers cloud storage, file synchronization, personal cloud, and client software. Users can store files in the cloud, synchronize files across computers and devices, and share files.
Skype is a software application for video chat and voice calls. It allows users to make video and voice calls to other users over the Internet. Skype also allows users to send instant messages, share files, and make video calls to landlines and mobile phones.
Google Drive is a file storage and synchronization service developed by Google. It allows users to store files in the cloud, synchronize files across devices, and share files. Google Drive also offers a variety of productivity apps, such as Google Docs, Google Sheets, and Google Slides.
All of these services allow users to create a shared folder metaphor using a Web service. This means that users can create a folder on their computer that is then synchronized with the cloud service. This allows users to access their files from any computer or device that has an internet connection.