What could prevent EnCase from detecting partition information during a hard drive acquisition using a Linux boot disk?

The capability of EnCase to detect partition information during a hard drive acquisition can indeed be influenced by the state of the drive and how that interacts with the operating system being used for the acquisition.

If the drive has been FDisked, meaning that the partitions have been deleted or removed, EnCase would not be able to detect the partition information. The partition table, which holds information about the partitions present on the drive, would be gone; hence, EnCase would not have access to any details about those partitions.

On the other hand, if the partitions exist but are not recognized by Linux, perhaps due to being formatted with a file system that Linux does not support or recognize, EnCase would also be unable to detect them. Different operating systems have varying levels of compatibility with file systems, and this affects the tools that rely on those systems' ability to read and interpret partition and disk information.

Both scenarios highlight conditions under which EnCase would fail to detect partition information. Therefore, selecting the combination of options that includes both the scenario where partitions are removed and where Linux fails to recognize existing partitions as the correct answer accurately encompasses the possible reasons for detection failure during the acquisition process.