Answer:
The correct answer will be option B-observation.
Step-by-step explanation:
A scientific question and hypothesis can have answers based on the observation and experiments supported by the experiments of other works.
In the given condition, the answer to the evolutionary question "why the whales have finger bones?" was answered on the basis of the observation that whales have evolved from the land animals in which the finger bones were present and were modified into flippers in whales which was supported by the concept of homologous structures given by Charles Darwin.
Thus, option B-observation is the correct answer.