Traditional classifications tended to take into account a) extinct organisms b) rna similarities c) dna similarities d) generals similarities in appearance

when it is at an intermediate population density

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.

ok yes, but what is the question? as soon as you ask the actual question i will answer it. : )