I can't choose who to kill.
I stopped listening to my teacher and just kept thinking about which girl to choose.
You chose a great Fugu costume.
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means "choose", so the verb version is to choose.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
You have the opportunity to choose. You choose, and a bright sign lights up reading "error" (えら).