Final answer:
An example of hardware fault tolerance is redundant hard drives in a server, which allow for continued operation in the event of a drive failure. This is known as RAID. Multiple-version programs, on the other hand, are a form of software fault tolerance, not hardware.
Step-by-step explanation:
The subject of this question relates to hardware fault tolerance, which is a concept in computer science and engineering that describes the ability of a system to continue operating properly in the event of the failure of some of its components. In regards to the options provided:
- Redundant hard drives in the server (option a) is an example of hardware fault tolerance. This practice, known as RAID (Redundant Array of Independent Disks), ensures that if one hard drive fails, another can take over without loss of data or service.
- Multiple-version programs (option b) relate to software fault tolerance, which involves having several versions of software running in parallel to check for errors and inconsistencies.
Therefore, the correct answer to the question is: a. Redundant hard drives in the server.