Answer:
B- The organism cell structure
Step-by-step explanation:
The options you can rule out:
A- The organisms’ reproductive rate isn’t important since it’s just telling how fast the organism can grow, and it doesn’t provide information on where to assign it to a domain and kingdom.
C- The organisms’ population size of the organism isn’t important since it just shows how many there are, but it doesn’t provide information on where to assign it to a domain and kingdom
D- The organisms’ social behavior can be important (since it’s talking about how the organism acts and behaves toward other organisms, but it isn’t important on where to assign it to a domain and kingdom
Hence,
If scientists discovered a new type of organism, Option B: knowing the organism cell structure is most important, because it goes in dept on what the specific formation of the organism. Looking at the cell structure provides information on what where to assign is to a domain and kingdom.