Can someone please help me? I don't understand what the whole G A T C thing is, I am confused on what they do, and what it means when my assignments have it like [AATCGAT or TATGGCAT] (<--Example)

What does it mean when they are sequenced like that?

According to the rna world hypothesis, rna acted as the genetic material and catalyzed reactions in ancient cells. what conclusion can you draw from this?               a.  this implies that dna and proteins aren't essential in cells today.    b.  this implies that rna can catalyze any chemical reaction that enzymes catalyze.    c.  this implies that if a cell has a problem with its dna, its rna can compensate for the damaged dna.    d.  this implies that dna and proteins evolved after rna.