Index and Data Cache Files

Assuming that the master pipeline has 5 fields, two of which are part of the join condition and that all fields are connected downstream to the next transformation.then How many fields are in the index and data cache files?
options:
a. 5 fields are in index and 3 in data cache
b. 3 fields are in index and 2 in data cache
c. 2 fields are in index and 3 in data cache
d. 2 fields are in index and 5 in data cache
what is the answer.??