Question

Why one should breathe through nose and not by mouth

Answer 1

the answer when we open our mouth all the impurities and all other insects go in our body and harm us but breathing through nose stops all the impurities ' dust and insects in the hair present in our nostrils. 
hope this will help u .

Answer 2

when we breath with our mouth some problems may occur in future like heart problem etc .due to polluted air