はあ

　１　はっきりNoと言えないとき使う。
  　　Used when it is difficult to say NO clearly.

　２　よく理解していないとき使う。（会話6）
  　　Used when one can't quite understand what the other party has said.

　３　聞き返すとき使う。
  　　Used when one can't get what the other party said and wants him/her to repeat what he/she said.