Which of the following titles do you choose for this article

A．Nobody has defined and recognized slang, although they are used by a generation after another generation.
B．Slang tends to be transient though they have found their way in dictionaries.
C．Having difficulty in defining slang and telling slang from similar things, people still use slang frequently.
D．Slang can be totally beyond the understanding of the old.

A．they use slang s which are out-of-date
B．they would like to be at the top of the fashion
C．they try to follow their children's steps
D．they want to follow the fashion even if they can not