Answer: The answer is A cell theory.
Explanation: For our cells to be as developed and complex as they are today a huge evolutional process was necessary. This process is explained in the cell theory
I think the answer is that pressure builds and causes the heart to work harder.
I don't know what your choices are, but I would imagine that the answer is the process of crossing over. Next time please provide the choices that you're given :)
The final phase the 5th phase I think