Question

What fundamental traits did Linnaeus use to separate plants from animals?

Answer 1

The ability to move independently.

Explanation:

Animals could move about on their own power and volition. Plants were fixed, or carried randomly by external forces.
https://www2.palomar.edu/anthro/animal/table_kingdoms.htm

Background:
http://www.ucmp.berkeley.edu/history/linnaeus.html
https://www.famousscientists.org/carolus-linnaeus/
http://bertie.ccsu.edu/naturesci/Evolution/Unit10Background/Linnaeus.html