Answer the following question given this paragraph: 

After the film is developed, any unexposed silver bromide must be removed by a process called “fixing”; otherwise, the entire film would turn black with additional exposure to light. Although silver bromide is insoluble in water, it is soluble in a dilute solution of sodium thiosulfate (Na2S2O3; photographer’s hypo) because of the formation of [Ag(S2O3)2]3− ions. Thus washing the film with thiosulfate solution dissolves unexposed silver bromide and leaves a.


Q: After the film is developed, any unexposed silver bromide must be removed by a process called what?

 Choices:

- watering

- sweeping

- washing

- fixing

A:
fixing
