The first eight bars of this song clearly serve as an expository function. It has clear cadences that show a period and is repeated.
I guess the next set of sixteen bars (two identical eight bar periods) has to have a transitional function since it is completely different from the expository section.
The next eight bars after this are a development of the main theme because it is similar to the main theme but has different dynamics, lack of doubled octaves in the melody and a little embellishment.
The final eight bars is extremely similar to the first eight bars, but has a clearer cadence at the end so this period has a terminative function in showing the listener that the song is really over.
I hope I wasn't supposed to say anything more than this. Just following directions.