The two sentences that are contradictory statements in a dichotomous key are called

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

regents of the university of california v. bakke, 438 u.s. 265 (1978), was a landmark decision by the supreme court of the united states. it upheld affirmative action, allowing race to be one of several factors in college admission policy.