Gas (oxygen) exchange takes place across the walls of the

Which of the following statements is true of enzymes? a)they dont provide an active site for substrates to bind in a reaction b)they act on a specific type of substrate in a reaction c)they unusable after a reaction d)they change shape after a reaction

Explain how scientists use geologic time to determine the age of landforms.

Is dna the same in every cell in the human body explain your answer