Why Does Sinnott-Armstrong Discuss the "Universalizability Principle

Why does Sinnott-Armstrong discuss the "universalizability principle?"

A) To argue that the principle, if it were plausible, would entail that individuals are morally obligated to reduce their greenhouse gas emissions.
B) To argue against the principle by pointing out its implications for individuals' right to emit greenhouse gases.
C) To argue for the principle on the grounds that only it can explain individuals' moral obligation to reduce their greenhouse gas emissions.
D) To argue that the principle does not entail an individual obligation to reduce greenhouse gas emissions.