How can the Cretaceous system be subdivided?
This does seem like there are some instructions or details missing, because as shown it's relatively simple, except for the convoluted wording.
You have two wells: Long Island and Oooguruk. These are like slices taken out of the crust of the Earth. Not all slices are going to be the same; some regions might have more or less complete pictures of the full sequence. For example, one well might have no records at all from, say, the Maastrichtian, because no sediment was laid down in that location during that time period.
You're given a list of fossils, the times in which they existed, and the wells (slices of the crust) they are associated with. The connection to make here is which parts of the Cretaceous each well represents. Put it another way: if we know the Fossil-Stage relationship, and we know the Well-Fossil relationship, we can establish the Well-Stage relationship.
Oooguruk contains fossils A, B, C, D, G, K, O and P.
Relating these to the Fossil-Stage chart:
B: Maastrichtian and Campanian
C: Campanian and Santonian
D: Campanian, Santonian and Coniacian
K: Albian (notice that here we've skipped the Cenomanian stage between G and K)
O: Barremian (here we've skipped another period, the Aptian)
So, we can reasonably conclude that the Oooguruk well contains Maastrichtian, Campanian, Santonian, Coniacian, Turonian and Albian stages in a fairly continuous record. It then skips the Aptian, resuming with Barremian records, and then terminates, with no records from the Hauterivian, Valanginian or Berriaisian.