You dont need to root your device to check running apps on Android and close or force stop them. See running apps on HTC One and choose to close applications from this path:
1. Open "Settings" App
2. Open "Apps"
3. Swipe right to go to "Running" apps
4. There you can see the list of running apps on your phone
5. Tap each of them and hit "Stop" to close them (You may not be able to close the entire open apps)