Final answer:
The most likely step to take advantage of the features offered to NTFS drives without losing the existing data is to backup the data, format to NTFS, and then restore the data.
Step-by-step explanation:
The most likely step to take advantage of the features offered to NTFS drives without losing the existing data would be option c: Backup data, format to NTFS, and then restore data.
This option ensures that the data is backed up before formatting the drive to NTFS. Once the drive is formatted, the data can be restored back to the drive, preserving the existing data.
Option a is also a valid step, but it involves copying the data to an external drive, formatting the hard drive to NTFS, and then copying the data back. However, this option involves an extra step and a larger risk of data loss compared to option c.