不懂！

My mum, sis and me were chatting in my living room and something happened....

Me: Jing, do you know..... ?
Jing: 不懂
And about 2 seconds later, we heard...
Ziqian: 不懂

All of us heard that and got a shocked! It was so distint and clear. We turned to him (my sis was carrying him) and asked him "are you saying 不懂?" He returned us with his usual cheeky smile... I have yet to recover from this shock...