During light reaction of photosynthesis, the protons of stroma are carried into lumen of thylakoid by the following 

I. Plastocyanin 

II. Plastoquinone 

III. Cytochrome ${\mathrm{b}}_6$f 

IV. Ferridoxin
 

• A

  I and II

• B

  II and III

• C

  III and IV

• D

  I and IV