Step 1: Understanding the sentence.
The sentence suggests that Sara made a quick decision, implying impulsiveness. "Impetuous" fits the context as it means acting quickly without thinking, often impulsively.
Step 2: Analyzing other options.
- Impervious means not affected or influenced, which does not fit the context of making a quick decision.
- Inarticulate means unable to express oneself clearly, which is unrelated to the context of decision
-making.
- Inerrant means free from error, which does not apply here.
Step 3: Conclusion.
"Impetuous" fits the context as it describes someone who makes hasty or rash decisions.
Thus, the correct answer is 2. impetuous.
Final Answer:
\[
\boxed{\text{The correct answer is 2. impetuous.}}
\]