Erin made a to join the air force when she left college. a. decider b. deciding c. decision d. decisive

c. decision

Explanation:

The correct answer is "decision." This is because the word is the only one that presents the correct part of speech, as well as the only one that makes sense in this context. The idea that the passage wants to transmit is that Erin made a choice about her future, and this choice implies joining the Air Force when she leaves college.