How many known presidents has the us had not including the one that got re elected.

43

Explanation:

there are 45 presidents in total you said the one who didnt get re elected so obama and clinton so in total without those two its 43 presidents

d is the correct answer.

b is incorrect because it makes food by itself

c is incorrect because us humans don't know how to produce their own food using the sun like plants.

a is incorrect because consumers can depend on carnivores for eating food for consumers to eat the dead organism. same thing with omnivores.