I was talking to someone and they asked me:
to which I responded saying:
My friend then told me that that sounded a bit strange, and it would have sounded more natural if I had responded with either one of these instead:
I don't quite get the difference in nuances between all of these, and I was hoping someone could help explain why the だ ending sounds weird, whereas the other two sound fine? Also, why is it that です without a よ after it is acceptable, whereas だ must be followed by a よ?