Answer: They are all genetically tractable
Step-by-step explanation:
Yeast, fruit flies, nematodes, mice or the small plant Arabidopsis have known genome i.e their entire genetic information is known to the scientific community, thus they are EASILY MODIFIED in genetic research.
Also, they are simple eukaryotes (having cells with defined nucleus) so they can explain the processes in the human eukaryotic cell during genetic research
Both reasons make them genetically tractable