Question

Nitrogenous waste are not excreted through lungs like CO2.Give reason

Answer 1

because their muscle is too soft and they cannot be safe from such harmful things

Answer 2

Nitrogen wastes, which form toxic ammonia, produced in the body must be excreted.

But the process of excretion is not like the way Co2 excreted form the body.  

lungs excrete the Co2 but not nitrogen waste, because lungs are not so powerful to excrete harmful wastes like this.

This is the reason through urine human excrete their nitrogen waste.