先生が推薦状を書いて___。
Q. Which honorific verb fits 'the teacher kindly wrote (for me)'?
Translation
My teacher kindly wrote a recommendation letter for me.
Explanation
くださる is the honorific form of くれる, appropriate because the giver (先生) deserves respect: 書いてくださいました. いただく would need the receiver as subject (先生に書いていただきました).