Which command displays all the files having the same name but different extensions? A. Dir filename.* B. Dir filename.ext C. Dir *.sys D. Dir *.ext

The correct answer is: A. Dir filename.*

The command Dir filename.* will display all the files in the current directory that have the same name but different extensions. For example, if the current directory contains the files file1.txt, file2.txt, and file3.exe, then the command Dir file* will display the following output:

file1.txt
file2.txt
file3.exe

The asterisk (*) is a wildcard character that matches any number of characters. In this case, it matches any character after the file prefix. So, the command Dir filename.* will display all the files in the current directory that have the name file followed by any number of characters and any extension.

The other options are incorrect for the following reasons:

• Option B, Dir filename.ext, will only display the files in the current directory that have the name filename and the extension ext.
• Option C, Dir *.sys, will only display the files in the current directory that have the extension sys.
• Option D, Dir *.ext, will display all the files in the current directory that have any extension.