instruction:
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.
question:
Four objects are on a wooden ramp. Which object is most likely to roll off the ramp if it is pushed gently?
(A) flat eraser (B) round ball (C) bent paper clip (D) wooden cube
answer:
B

question:
When manned space exploration began, NASA used the gravity assist concept so that spacecraft could conserve fuel. Which statement explains why the gravity assist concept was useful for spacecraft to successfully travel and return to Earth?
(A) It gave spacecraft a timed trajectory. (B) It ensured spacecraft would return home safely. (C) It was helpful in planning spacecraft trajectories. (D) It ensured spacecraft would avoid being pulled into the sun.
answer:
C

question:
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
answer:
C