INTERVAL BETWEEN

Whenever within a sentence you see the world INTERVAL make yourself very clear that it's talking about two parts so it has to be followed by "BETWEEN".

For e.g.

Because the economic cycle in the USA changes little during its twenty year interval between recessing , it is fairly easy for analyst to predict analogous trends in the stock market.
a) between recessing
b) of recessing
c) between its recessions
d) of it recessions
e) as it recesses

Since, its talking about the USA's economic cylce the pronoun should be "its", therefore answer is C.