why was it not deleted?

While deleting all files beginning with the letter a there was still the file Access.txt left.
Assuming that it had the correct ownership, why was it not deleted?

A.
Files with extensions need a different treatment.

B.
rm had to be called with the option -R to delete all files.

C.
The file Access.txt was probably opened by another application.

D.
The file Access.txt was hidden.

E.
Linux file names are case sensitive.