The primary function of the respiratory system is to supply blood with oxygen
The correct answer is B. unicellular.
Dinoflagellates are unicellular or multicellular, producers, and autotrophs, and apple trees are multicellular, producers, and autotrophs. All plants have numerous cells in them, so they can never be unicellular. The remaining characteristics they share with less complex organisms such as dinoflagellates.
A high specific heat enables organisms to resist temperature fluctuations.
Birds are an example of an animal that migrates, birds migrate south when it gets cold so they can be in warm weather.