Nikon d7000 focusing problem?

Ok my brother was toying around with it and now it doesn't focus anymore. How can I fix this?

Check AF/MF setting on the lens is set to AF, and that the AF/MF dial on the body is also set to AF, then press the button in the middle that dial and check the AF mode on the rear screen.

If all that fails momentarily remove the lens before reattaching it (with the camera powered off). See if that fixes it.

Failing everything, go into the menus and reset the camera back to it's default settings.