What is the role of water in the light reactions of photosynthesis?

Water parts goes into oxygen, hydrogen particles, and the electrons to replace the lost electrons of photosystem II in light-subordinate response. Next, as hydrogen particles go through ATP synthase, ATP is form to use in the light-free response. 

The rol of water in photosynthesis is to supply electrons for said redox reactions, that is, water intervenes as a source of electrons

Explanation:

Since the water molecule is a very weak reducing agent, its electrons must be energized by the photons of sunlight, so that they acquire enough potential to reduce the inorganic molecules mentioned carbon, nitrogen and sulfur. The energetization of water electrons is carried out thanks to chlorophyll, the typical green pigment of the plant world that acts as a receptor and converter of solar energy into chemical energy.

In addition to redox energy, most of the assimilation reactions of C, N and S require the energy input of ATP (adenosine triphosphate), the well-known energy currency of living beings. Therefore, the energy of the photons absorbed by chlorophyll is used not only to energize electrons in water, but also to make ATP from inorganic phosphate. This last reaction is known as photophosphorylation and is catalyzed by the ATP synthetase of the thylakoid membranes. Thus, photosynthesis can be considered to consist of two distinct and sequential phases. In the first place, the photooxidation of chlorophyll-dependent water, with the consequent production of assimilative power (high energy electrons and ATP), and secondly the assimilatory reduction of the primary bioelements thanks to the assimilatory power obtained in the previous phase

The right options are; makes food for all organisms, adds oxygen to the atmosphere, is a source of medicines and fibers, is a source of building materials and it provides animal habitat.

Photosynthesis is a process by which green plants and some other autotrophs use light energy in chloroplasts to generate carbohydrates (food) from carbon dioxide and water while oxygen is being released as a by-product. Photosynthesis is essential to all living organisms on earth because it is the main source of oxygen in the atmosphere. Photosynthesis provides animal habitat, it provides food for all organisms (directly for plants and indirectly for animals). Plants and trees produce their foods through photosynthesis and are used as medicines and fibers, and as building materials.