The correct answer is A. .app, because macOS applications packaged as .app files are typically self-contained application bundles. This means that all required application files are stored within a single directory that appears as one file in Finder. When the .app file is moved to the Trash, the application is effectively removed from the system.

According to the Quentin Docter – CompTIA A+ Complete Study Guide, macOS applications are commonly distributed as .app bundles, allowing for simple installation and removal. This design contrasts with Windows, where applications often install files across multiple directories and require uninstallers.

The Travis Everett & Andrew Hutz – All-in-One Exam Guide explains that dragging a .app file to the Trash is generally sufficient to uninstall the software, although some applications may leave behind preference files or caches. However, from an exam perspective, .app is the only option that supports this uninstall behavior.

The Mike Meyers / Mark Soper Lab Manual further clarifies that .msi and .exe are Windows formats, .rpm is used by Linux package managers, and .pkg installers often install system-wide components that require a formal uninstallation process.

Because .app files support simple drag-to-trash uninstallation, A is the correct answer.