Final answer:
Charles Lyell believed that the Earth formed over 2 billion years ago, which changed the understanding of the Earth's age and geological history. Hence, b) is correct.
Step-by-step explanation:
Charles Lyell discovered evidence to support his theory that the Earth had formed long before humans originally thought.
Lyell believed that the Earth formed over 2 billion years ago. Prior to Lyell's work, the majority of natural historians believed the Earth was less than 6,000 years old.
By altering the suspected age of the Earth to millions of years, Lyell changed the framework within which scientists viewed the geological past.