Complex password in Windows Server 2008

Recently, there is a question about password complexity in Windows 2008 Domain.

Windows 2008 is disabled by default and domain is enabled by default.

Now, the complextiy means:

1) Passwords must contain characters from three of the following four categories:
a. English uppercase characters (A through Z).
b. English lowercase characters (a through z).
c. Base 10 digits (0 through 9).
d. Non-alphabetic characters (for example, !, $, #, %).

It is smart enough to get three out of four...it puzzled me for a while.