Splitting of water is associated with

1.  photosystem I

2.  lumen of thylakoid

3.  both photosystems I and II

4.  inner side of thylakoid membrane

The thylakoid is a photosynthetic unit in the chloroplast. It is a membrane bound structure. The membrane has photosystems I and II embedded in it in the form of chemicals and molecules. Splitting of water is associated with PS-II which occurs in presence of Mn2+ and Cl- ions on the inner surface of thylakoid membrane.
2H2O Cl-Mn+ 4H++O2+4e 

Photosystem I and II are associated with light reactions.
Page 213, XI NCERT