Explain the purpose of a molecular clock and the properties that a section of protein must have to be used in this way. < really need !

Look at lesson it says

A measure of evolutionary change over time as the molecular level that is based on the theory that specific DNA sequences or the proteins they encode mutate at constant rates

Now put into your own words

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correct answer is a. and d.

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.