Since this word is made up of a single kanji, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word:
It's hard to start a mnemonic with the word "thing" or "action," so let's continue off the kanji mnemonic where you've put a cross in the mouth of a wolverine. Why did you do it? You knew that feisty wolverine was going to eat your coat (こと).
Why do you think Ms. Sumomo wears so many pink clothes?
I often have trouble understanding what my junior colleague is saying.
I’m sorry but I’ve been busy recently because I have a lot of things to do.