In the earliest stages of development, all four organisms have a knobby head, gill slits, and a tail. These similarities tell us that all four of these organisms have a common ancestor.
Answer:
A. The complementary shapes of an enzyme and a substrate
Explanation:
The Lock-and-Key model was made to show how an enzyme's active zone fits a substrate and how they bond together. It correlates just like a lock and a key; you have to have the correct-shaped key in order to open a lock. Same process of thought with the enzymes; you must have the same shape for both in order to bind together,
