Recall that a group $G$ is called indecomposable if it cannot be written as a direct sum of two proper normal subgroups.
My Question is "Is additive group of complex numbers indecomposable?
I stuck in proving this. I searched it a lot more on internet. But, I could not find any thing regarding this Question. Please give a short proof or a relevant source where I can find its solution. I will be highly thankful to you.