Answer;
Key
A sorting device that is useful in classifying by observation is a key.
Explanation;
Classification key or taxonomic key is a device that is used by scientists to identify unknown organisms.
They are constructed so that the user gets a series of choices about the characteristics of the unknown organisms.Thus, by making the correct choice at each step, one is led to the identity of the specimen.
Therefore, keys can be used to identify a living organism or determine which group it belongs to by answering questions on the key about characteristics of living things.