For Hundreds of Millions of Years the Surface of Venus

Multiple Choice

For hundreds of millions of years the surface of Venus, it is believed, was hot and humid, with the pressure of its thick water vapor-dominated atmosphere large enough to prevent liquid water from boiling away. What happened to disturb this equilibrium, raise the temperature, and boil away the liquid water?

A) Radioactivity in minerals in the mantle raised the surface temperature.
B) Bombardment by heavy impactors raised the surface temperature.
C) The Sun got hotter.
D) Friction with the dense atmosphere slowed the rotation of Venus so that the Sun was able to raise the temperature of the daytime hemisphere well above the boiling point.