I have been (1)/ working in this organization (2)/ since three years. (3)/ No error (4)

Answer

3

Explanation

for will replace since because since is used while specifying the starting point. for is used while specifying the amount of time (how long). Look at the examples given below: She has been dancing since she was 5 years old. She has been dancing for a long time. Hence, for three years is the right usage.