Why does Chrome keep opening on its own?

Recently,

I tried to download MS Office 2015 Preview for Mac OSX from microsoft’s official website. When i realized as I was downloading that it required Mac OS Yosemite, but I have Mavericks, I quit chrome (Cmd + Q)

Now whenever I boot up my mac, Chrome opens by itself. I’ve tried deleting all of Chrome’s memory, and deleted and reinstalled Chrome, but the problem is still there. Chrome keeps opening by itself.

What is wrong with Chrome? What can I do?