I think it's important to concentrate yourself to complete what you are doing, but if you have also new ideas try to develop them into something useful
They did not have big differences between social classes and had extensive trade with nearby people<span>
</span>
The correct answer is D, white blood cells.
We know that red blood cells deliver nutrients and are not apart of the immune system; platelets are responsible for coagulation, which has nothing to do with the immune system, and plasma is a substance that, again, has nothing to do with immunity. White blood cells are the only things that fight disease (antibodies are white blood cells)!
I hope I helped!
(By nothing I meant very little to none).
They are both ectothermic, but fish have gills, and reptiles have lungs.
