Sodium thiosulfate (Na2S203) solution is indeed used in photography, but it is important to understand its specific role in the process. Let`s dissect each option to better understand them:

1) Option 1 suggests that sodium thiosulfate removes reduced silver. This is not completely accurate. Sodium thiosulfate actually acts as a fixing agent in photography, removing unexposed silver halide crystals from the photographic film or paper. It does not remove already reduced silver.

2) Option 2 states that sodium thiosulfate reduces silver bromide (AgBr) grains to silver. This is incorrect. Silver bromide grains are already reduced during the film development process using a developer solution. Sodium thiosulfate is used to fix the remaining unexposed silver halide that has not been reduced.

3) Option 3 correctly states that sodium thiosulfate removes undecomposed AgBr as a soluble silver thiosulfate complex. This is the actual role of sodium thiosulfate in photography. It reacts with the unexposed silver halide to form a soluble complex called silver thiosulfate, which can be easily washed away.

4) Option 4 suggests that sodium thiosulfate converts metallic silver