Diferentiating o2 sensors?

I am replacing an o2 sensor,but not real sure which 1 is bank 1 sensor 2? anyone help?

Its the rear o2 sensor

I am replacing an o2 sensor,but not real sure which 1 is bank 1 sensor 2? anyone help?
bank 1 is on the manifold bank 2 is cat

bank 1 sensor 1, first o2 on cylinder with the number 1 spark plug, bank 1 sensor 2 is second sensor on same side. bank 2 sensor 1, 1st sensor on opposite side, bank 2 sensor 2 is second sensor on this side.