$$A$$, $1$ to $5$ $$=\frac{1}{5}$$, $$\frac{0.5}{1}=\frac{5}{10}=\frac{1}{2}$$, so wrong.  $$B$$, $$\frac{1}{5}=1:5$$, so true.  $$C$$, $5$ to $10$ $$=\frac{5}{10}=\frac{1}{2}$$, so wrong.  $$D$$, $$1:5=\frac{1}{5}$$, $$\frac{5}{10}=\frac{1}{2}$$, so wrong. 
Which of the following groups has equivalent ratios? 

(1) $1$ to $5$, $\frac{0.5}{1}$ 
(2) $$\frac{1}{5}$$, $1:5$ 
(3) $\frac{1}{5}$, $5$ to $10$ 
(4) $1:5$, $\frac{5}{10}$ 