It relates to the meaning of the pores of skin because it lets in and out only certain things.
I hope this helps, Sweetie.
Long chains of amino acids used for building, repair, and maintenance.
For example, if the acceleration is zero, then the velocity-time graph is a horizontal line (i.e., the slope is zero). If the acceleration is positive, then the line is an upward sloping line (i.e., the slope is positive). ... If the acceleration is great, then the line slopes up steeply (i.e., the slope is great).