Đáp án đúng: C
Giải chi tiết:\(\begin{array}{l}\frac{{315}}{{10}} = 31\frac{5}{{10}} = 31,5\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{{6308}}{{100}} = 63\frac{8}{{100}} = 63,08\\\frac{{121}}{{10}} = 12\frac{1}{{10}} = 12,1\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{{505}}{{100}} = 5\frac{5}{{100}} = 5,05\end{array}\)
Chọn C.