Final answer:
The d. Darwinian theory provides the best explanation for the pace of evolution through the process of natural selection.
Step-by-step explanation:
Among the given options, the d. Darwinian theory provides the best explanation for the pace of evolution. Darwin's theory of evolution by natural selection proposes that species gradually change over time through the process of natural selection.
This theory is supported by various evidence such as the fossil record and the observation of adaptations in different species. Additionally, the theory of evolution can explain the vast diversity of life on Earth and how species have evolved to suit their environments.