The best explanation for the theories of natural selection is that

Explanation

The question is asking for the best explanation for the theories of natural selection. Natural selection is a process where organisms with certain traits are better adapted to their environment and are more likely to survive and reproduce. The organisms that are better adapted are more likely to pass on their genes to the next generation, while those that are less adapted are less likely to survive and reproduce. From the options given, the correct answer is option C: organisms compete for resources and better competitors survive and thrive. This means that in any environment, there are limited resources and organisms have to compete for them. Those that are better adapted or have better traits are more likely to get the resources they need to survive and reproduce. Over time, these traits become more common in the population, leading to evolution. Option A, which states that all organisms have equal capacity for survival in their habitats, is incorrect because different organisms have different traits that may make them more or less adapted to their environment. Option B, which states that organisms have varying capacities for survival in their habitats, is partially correct, but it fails to mention the important role of competition in natural selection. Option D, which states that habitats allow only organisms that will not have to compete for survival, is also incorrect because all organisms have to compete for resources to some extent. It is important to note that natural selection is just one of the mechanisms of evolution, and that there are other factors such as genetic drift and gene flow that also play a role in shaping populations over time. To learn more about this, please read the relevant sections of the recommended textbooks.