The correct answer is A. The principle of uniformitarianism
Step-by-step explanation:
Both James Hutton and Sir Charles Lyell were important geologists during the 18th century as they focused on understanding the composition of Earth, the universe and the way this has changed over time. Besides this, in this field, they contributed to the principle of uniformitarianism that states general laws and principles that exist nowadays on Earth and Universe, also operated in the past. In the case of James Hutton, his work was based on observations related to the formation of Earth as well as geological arguments. Similarly, Sir Charles Lyell supported this principle based on the history of Earth; also, he formally explained this principle through his book Principles of Geology in 1830.