I'm terribly sorry — I'm terribly sorry for the wait.
I apologize — I apologize for the trouble.
I'm really sorry — I'm really sorry about this.
やってみよう: Amina: There is a problem with my room. Hiroshi: ___ What is wrong? Hiroshi works at the hotel and wants to apologize. Which fits? (I'm terribly sorry. / Excuse me, but / I'm not happy with) 答え: I'm terribly sorry. — I'm terribly sorry は謝罪の表現なので、Hiroshi の返答に合っています。Excuse me, but や I'm not happy with は苦情を言うときの表現なので、謝罪にはなりません。
丁寧に苦情を伝える
角を立てずに苦情を言うときは、まず Excuse me, but で切り出し、問題になっているものの前に There's a problem with や I'm not happy with を続けます。
Excuse me, but — Excuse me, but this is cold.
There's a problem with — There's a problem with my room.
I'm not happy with — I'm not happy with the noise.
やってみよう: Sofia: How is everything in your room? Diego: ___ the noise. I can't sleep. Diego wants to complain politely about the noise. Which fits? (I'm not happy with / I apologize / I'm really sorry) 答え: I'm not happy with — I'm not happy with は丁寧な苦情を切り出す表現なのでぴったりです。I apologize と I'm really sorry はどちらも謝罪の表現なので、苦情を伝えることはできません。