You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

Sir Isaac Newton stated that every object in the universe attracts matter. The attraction depends on the mass of an object and the distance between the objects. What type of force did Newton describe?  
 (A) centripetal force (B) generalized force (C) centrifugal force (D) gravitational force
D

A car runs out of fuel while traveling on a level road and eventually comes to a stop. Which of the following best explains why the car stops?  
 (A) Some of the energy of the car was lost to friction. (B) Some of the energy of the car was destroyed. (C) The amount of kinetic energy increased. (D) The amount of useful energy increased.
A

Which event is most likely to increase the genetic variation in a population of organisms?  
 (A) improved hunting techniques (B) greater environmental stress (C) increased immigration (D) introduced predators

C