Mitosis is a process that makes DNA synthesis
Provided that there's no diagram, most molecules have particular areas on the molecules, called the "active area" that act as a lock to a particular substrate's molecular structure, providing the key.
An enzyme's active area is only able to be "unlocked" by a certain substrate's "key".
Protein expression refers to the way in which proteins are synthesized, modified and regulated in living organisms.
Hope this helps :D
The answer is A. A water molecule
because you’re removing H2o