How does investigating densities of different objects allow us to understand the world better?

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

Which statement is true about the cell theory? a) it is well-supported by evidence. b) it is unchangeable and permanent.

How does natural selection change thephenotypes within a population over time?