答案1
Look for any Background services that is running.
Use the Task Manager (Right Click on Task Bar at the bottom of the screen, then click on Task Manager), Go on "Network" Tab, and see what is taking all that Bandwidth. on the Task Manager Network tab, click "Resource Monitor", which shows the individual connections and program that owns each. (Thanks to @Ben_Voigt)
It's normal to have a constant use of the bandwidth, but it shouldn't overload it.