答案:By CONTEXT OF SITUATION, Firth meant a series of contexts of situation. each smaller one being embedded into a larger, to the extent that all the contexts of situation play essential parts in the whole of the context of culture. It can be summarized as:
(1) the relevant features of the participants, persons,personalities
(a)the verbal action of the participants
(b)the non-verbal action of the participants
(2) the relevant topics, including objects, events, and non-linguistics, non-human events
(3) the effects of the verbal action.
Firth here seemed to suggest the creativity and diversity of linguistic idiosyncrasy(特性) in language use. And his emphasis is quite similar to “ who speaks(or write) what language(or what language variety) to whom and when and to what end” by Fishman