In the 1800s, Lord Kelvin Estimated the Age of Earth

Multiple Choice

In the 1800s, Lord Kelvin estimated the age of Earth, utilizing a number of assumptions. Which wrong assumption was the primary reason why his estimate (approximately 20 million years) was so wildly inaccurate?

A) Earth was once hotter than it presently is today.
B) Earth may have been molten when first formed.
C) No new heat has been added to Earth since its initial formation.
D) Earth would lose heat over time through radiation into outer space.