Select the following statements of proportion that are true
 
(i) \(​4​ : ​7​ :: ​12​ : ​21​\) ​
 
(ii) \(​8​ : ​3​ :: ​24​ : ​9​\) ​
 
(iii) \(​7​ : ​11​ :: ​12​ : ​11​\) ​