Which of the following is used on the client to boot a Linux system from a TFTP server?

HTTP is an application-layer protocol used for web content transfer and is not involved in TFTP-based network boot environments.

GRUB is a bootloader that runs after an initial boot image has already been loaded into memory; it does not initiate the client-side TFTP network boot process.

EFI (Extensible Firmware Interface) is a firmware specification for system initialization that can support network boot scenarios, but PXE is the specific standard protocol used for TFTP-based network booting.

PXE is a firmware-level client standard built into network adapter firmware that uses DHCP to obtain a network address and TFTP to download a boot image from a remote server. It operates before any OS is loaded, making it the specific technology used on the client side to initiate a network boot from a TFTP server.