It is more realistic to consider food webs, a more complex representation than a food chain. the chain does not take acocunt of all contributors. the producer will consume several foodstuffs, the species to be eaten will be consumed by more than one other species.
The web takes into account contributors that are part involved in one chain, and part involved in another. the ecosystem is always more complex than a simple linear construction can convey. So although option 2 is correct, option 4 gives more useful information about the ecosystem.