When a wire is stretched to double its length: 
(i) its radius is halved 
(ii) strain is unity 
(iii) stress is equal to Young's modulus 
(iv) Young's modulus is equal to twice the elastic energy per unit volume

• A

   (i, ii) 

• B

  (i, iii) 

• C

  (ii, iv) 

• D

  (ii, iii, iv)