Which of the following is the best definition of a scientific theory? A.
a broad, well-supported explanation of related observations or events
B.
a description of a natural phenomenon that is always observed to occur under specific conditions
C.
a plausible answer to a scientific question that is used to guide research
D.
a highly tentative statement about the natural world that is likely to be significantly changed or discarded

Describe the structure of amino acid, including what makes amino acids different from eachother

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.

Animal cells have which of the following characteristics? select all that apply.