Given your comment that there are 4 blues and 4 yellows, the answer would have to be C) probable.
It's not A) certain since it's not 100% guaranteed that it will land on yellow, because there's also blue, and it's not B) because for it to be impossible to land on yellow there would have to be no yellows (and, well, there's yellow). Lastly, it's not D since there's the same number of each color, it's not less likely to land on one over the other.
