In the given picture is the highlighted part true ..? Please explain with precision.

Dear student. As we are very familiar with the organs involved in excretion. So, the organs involved are kidney , lungs , skin, liver ,etc . So, lungs are respiratory as well as excretory both . Because while during respiration the lungs perform main function is to help oxygen from the air we breathe enter the red cells in blood . And the lungs also help the body to get rid of co2 gas when we breathe out . As the paragraph is saying us to not confuse with removal of wastes from rectum is called excretion . Thats why its is saying co2 not as excretion system because lungs does not remove undigested food from rectum . Regards