Answer:
A. Used to find extraterrestrial life, size and area of a planet / star.
Step-by-step explanation:
Drake equation is the probability argument used to estimate the number of active, extraterritorial civilizations in a milky way or number of communicating civilizations in the cosmos or more simply put, the odds of finding intelligent life in the universe.
Life existing on earth is due to the habitable zone.The region on the solar system where the temperature is in this range, is called the habitable zone. if a planet is too far away, the atmosphere will be cold and dry, and Carbon levels will remain high to the point that they would be toxic to Earth animals.