How to close running app ?

[bicture]

Did any options in these rom to kill running app ?

I cant find it.

and if dont have , how to close running app ?

thanks

[rapesauce]

Hold the back button on your phone till it closes

[tolymatev]

Press and hold home button and press kill all to kill all apps

[|0xD34D|]

While the app is open, you can press and hold the back button for a few seconds. This will cause the app to be shutdown.

[Stanley]

Hold the back button on your phone till it closes

I had flash the newest version, but I can't find the back button in any apps, how can make it available?, I can't closed and back to home.