Alvin is studying a model of the chemical structure of a common nucleic acid. He observes that the nucleic acid consists of four nitrogenous bases: adenine (A), cytosine (C), guanine (G), and uracil (U).

Alvin's observation most strongly supports which of these conclusions?

In trying to determine whether dna or protein is the genetic material, hershey and chase made use of which of the following facts? a) dna contains sulfur, whereas protein does not. b) dna contains phosphorus, whereas protein does not. c) dna contains nitrogen, whereas protein does not. d) dna contains purines, whereas protein includes pyrimidines.