The correct answer is: B. 6.0
MS-DOS 6.0 was the last version of MS-DOS to be released separately. It was released in 1993 and included a number of new features, such as support for long file names, a memory manager, and a disk defragmenter.
MS-DOS 6.11 was released in 1994 as a minor update to MS-DOS 6.0. It included a number of bug fixes and performance improvements.
MS-DOS 6.22 was released in 1994 as the final version of MS-DOS. It included a number of new features, such as support for FAT32 file system, a command-line editor, and a networking stack.
MS-DOS was a family of operating systems developed by Microsoft for IBM PC compatible computers. It was the first widely used operating system for IBM PCs and remained popular until the mid-1990s, when it was largely replaced by Microsoft Windows.