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?
A. The nucleic acid is a form of RNA, and is not DNA.
B. The nucleic acid is either mRNA or rRNA, but not tRNA.
C. The nucleic acid is either RNA or DNA.
D. The nucleic acid is DNA, and is not RNA.

How do you think earths interior affects what is happening on the surface? 2. how do fossils support the continental drift hypothesis? 3. how does sea- floor spreading support the hypothesis of continental drift? 4.what do scientists observe when they studied the magnetic fields of rocks on the sides of mid-ocean ridges? 5. what is a tectonic plate ? 6. explain mantle convection 7.how can movements of the continents affect earths climate? 8. what occurs during drifting?