I need help don’t know what to put

How many variables are altered in a good experiment? a.1 b.0 c.2 d.3

What function does the limb sever in each animal? how are the limb bones of the four animals similar? based on these similarities what can be inferred about the evolution of the four animals.

Error analysis: what might be the reason that some of your percentages didn't exactly match your predicted results? gametes aren't responsible for inheritance. mice don't have large litters, so the sample size was not large enough. the wrong type of mice were used.