"I don't know"

Every time we ask Eva a question, her response is "I don't know" followed by the answer. For example:

Q. "What did you have for lunch today, Eva?"
A. "I don't know... hot dish"
(BTW, she always says she has hot dish for lunch, and I know perfectly well that she doesn't have it every single day despite her claiming she does.)

Q. "What shape is this table, Eva?
A. "I don't know... circle."

Q. "What color is this, Eva?
A. "I don't know...red."

Every single question is always preceeded with the words "I don't know." I have been paying attention to her, trying to figure out where she's getting this from. I was thinking, maybe Mom or David are saying this a lot to her, but when I listened to them, I didn't really hear them saying this. So, I thought, maybe she's hearing it at daycare. But, whenever I pick her up, the only one I hear saying it is Eva. And she always says the answer following "I don't know" so I don't think she even knows what it means, she just thinks you have to preceed every answer with it. In any case, I have been trying to figure it out because it is a strange quirk and I want to know who she's getting it from. So... this morning, I'm putting Eva's socks and shoes on her when she points in the general direction of the entertainment center and asks me "What's that, mommy?" There are lots of things on the entertainment center and it takes me a minute to figure out what she's pointing at before I just guess and give her an answer. Yes, I hear coming out of my very own mouth, "I don't know...the remote."