"개가 집에 옵니다."
Translation:The dog comes home.
its just how Korean pronunciation rules work. Its like irregular verbs in English, or the silent P in Pterodactyl. The P isnt silent in every word, thats just how it is. Im afraod theres nothing you can do except read through online articles or other comment sections in here. I also reccomed the book Korean for Beginners - Mastering Conversational Korean by Kyubyong Park and Henry J Amen III
Duolingo, just let me understand you. First you say a certain phrase is correct then you say it is wrong, you give me certain options only to say those are wrong and then showing me the exact same phrase as correct. Looking at the forum I'm not the only one that keeps facing this problem