refers to the subject matter of the discourse
a- filed
b- fail
c-filing
d-all the above



--------------------------------
refers to the role being played by the speaker
a- Tenor
b- Tiner
c-Tanor
d- all the above

---------------------------------
refers to the medium of communication, e.g. speech or writing
A-Mode
B-Made
c-Model
d- all the above


from L 5