Which of the following macOS utilities uses AES-128 to encrypt the startup disk?

fdisk is a command-line utility used in Unix-like operating systems for disk partitioning, not for full disk encryption.

Diskpart is a command-line utility in Windows for managing disk partitions, and is not used on macOS.

Disk Utility is a macOS application for managing disks, volumes, and file systems, including formatting and partitioning, but FileVault is the specific feature for full disk encryption.

FileVault is the native macOS full disk encryption feature that uses AES-128 or AES-256 encryption to protect the data on the startup disk, ensuring all stored information is secure.