Which of the following is a cloud storage service?

Cloud storage services let a user save files on remote servers over the internet and access them from any connected device. This is different from a search engine, which helps users find information on the web, or a design tool, which is used to create graphics, since neither of those is built to store and sync a user's personal files.

Yandex is primarily a search engine and internet services company, DuckDuckGo is a privacy-focused search engine, and Adobe XD is a design and prototyping application. Drop Box, by contrast, is a dedicated cloud storage service: it lets users upload files to remote servers, keep them synchronised across devices, and share them with others through generated links.

The exam distinction to hold onto is function, not just familiarity: a cloud storage service is defined by its job of storing and syncing files remotely, which only one of the listed options is built to do.