Andrew works as a System Administrator for NetPerfect Inc.

Andrew works as a System Administrator for NetPerfect Inc. All client computers on the network run on Mac OS X. The Sales Manager of the company complains that his MacBook is not able to boot. Andrew wants to check the booting process. He suspects that an error persists in the bootloader of Mac OS X. Which of the following is the default bootloader on Mac OS X that he should use to resolve the issue?