Which highly reactive gas was probably absent from the earth's primitive atmosphere?

Which stage of the cell cycle usually takes the longest?

The diagram shows the structures of horse and cat forelimbs. what does the diagram suggest about the evolutionary relationship between these two mammals? a. they have homologous structures, indicating a common ancestor. b. they have analogous structures, indicating a common ancestor. c. they have homologous structures, indicating that they do not have a common ancestor. d. they have analogous structures, indicating that they do not have a common ancestor.

Which describes fat? a: a carbohydrate that produces energy b: a nucleic acid that directs cell function c: a lipid that stores energy d: a protein that speeds up a chemical reaction