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 to decide. You have two keys (き) in front of you. You have to decide on one of them and use it to unlock the door to get away from the monster. Why do monster attacks always come down to keys and doors?
Have you decided what you’ll do after graduating from university?
I'm too hungry to decide what we eat, so it's your choice where we go, Yui.
How do people decide what they’re going to do for the rest of their lives? There are so many jobs to choose from.