**Correct option is (A) 9: 11**

Mean of first 10 whole numbers \(=\frac{0+1+2+....+9}{10}\)

\(=\frac{9\times10}{20}=\frac92\)

Mean of first 10 natural numbers \(=\frac{1+2+3+....+10}{10}\)

\(=\frac{10\times11}{20}=\frac{11}2\)

\(\therefore\) Their ratio \(=\cfrac{\frac92}{\frac{11}2}\)

\(=\frac9{11}\) = 9 : 11