You are given a science question (hard-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: Two forms of boron are naturally occurring, boron-10 and boron-11. What difference exists between a boron atom with a 10 atomic mass units (amu) and a boron atom with 11 atomic mass units (amu)?  
 (A) amount of neutrons (B) number of electrons (C) size of protons and neutrons (D) size of electrons and electron cloud

Answer: A


Question: A tropical rain forest contains many tall trees. Smaller plants with large leaves grow at the base of the tall trees. The large leaves are most likely an adaptation of the plant due to which condition?  
 (A) lack of sunlight (B) lack of oxygen (C) lack of water (D) lack of food

Answer: A


Question: Manuel wants an area in the yard to wash the dog without making mud puddles. He wants to put something on the ground that water passes through easily. Which of these materials would be the best for him to use?  
 (A) clay (B) plastic (C) soil (D) pebbles

Answer:
D