a/an 与职业名词的搭配 — 英语填空题

猜职业，再填冠词。根据句子提示猜出职业，并在横线上填 a 或 an：1. Sam works in a hospital and helps sick people（病人）. He is ___ doctor. 2. Lily can fly planes very well. She is ___ pilot. 3. Ben draws beautiful pictures for a museum. He is ___ artist. 4. Kate puts out fires（灭火）. She is ___ firefighter.