Answer:
a
a process that selects variations to help with survi al and that spreads the variation to more offspring
Explanation:
the weak don't survive the strong thrive
This is active transport so the ions go against the concentration gradient. This means that the ions will travel from the place where there are less sodium ions(from the inside of the cell) to the place where there are more sodium ions (to the outside of the cell).
There are many ways to do this. You can either create a close approximation to what you think are the most relevant variables and hope your idea about the relevant variables was true.
Another way would be to do different kinds of experiments and hope you can deduce information from those experiments onto the subject that you would like to find an explanation for.
