Answer: Option (C)
Explanation: According to the law of Uniformitarianism, the geological processes that has been taking place now must have taken place in the past, and will also take place in future, at a constant speed, in long term.
Darwin suggested that the same Uniformitarianism process takes place in case of living beings also. According to him, these living creatures undergoes evolution and in this process, gradual changes in the organisms occurs being a long-term continuous process.
Thus the correct answer is option (C).