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:
Some types of bacteria can only live where oxygen is not present. These bacteria were well adapted to life on Earth over 2 billion years ago. Which of the following changes caused many of these bacteria to become extinct?  
 (A) the slow movement of tectonic plates (B) the varying temperatures of each season (C) an increase in volcanic activity under the oceans (D) an increase in the number of photosynthetic organisms
answer:
D


question:
What is the downward movement of water through pores and other spaces in soil due to the force of gravity?  
 (A) percolation (B) evaporation (C) precipitation (D) condensation
answer:
A


question:
Why do multicellular organisms need transport systems?  
 (A) Most have cells that are not able to exchange gases with the outside environment. (B) Most have cells that are unable to grow and survive in their environment. (C) Most have cells that need food from sources outside their environment. (D) Most have cells that require more energy to survive than single-celled organisms.
answer:

A