Task: Question Answering
Input (English): A scientist designs a mathematical model of the rock cycle. The model predicts how changes in Earth processes will affect the amounts of different types of rock on Earth. Which quantity should stay the same as Earth processes change?  
 (A) the average rate at which Earth rotates (B) the average distance of Earth from the Sun (C) the total number of inactive volcanoes on Earth (D) the total amount of material on Earth
Output (English): D