March 10th question

Consider the bipartite network in which the nodes $A$ are animals and the nodes $E$ are environments. If an animal $a$ lives in an environment $e$, then there is a link between $a$ and $e$. Take the following image as an example of part of this network.

If a scientist wants to know possible interactions among animals, they need to know which ones live together. One way to determine this it to:

1. Get all nodes of $A$, only the ones with the same degree live in the same environment
2. Calculate the probabilistic distribution of degrees, if $p_k$ is the same for two values $k_1$ and $k_2$, then the nodes of $A$ with degree $k_1$ live together with the ones of $k_2$
3. Check which nodes of $A$ are connected, if they are, they share the same environment
4. Calculate the projection $A$, if two animal nodes are connected in the projection, then they share the same environment
5. None of the above