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.

Some scientists have suggested that the Moon was formed when a large body struck Earth and broke off a piece of Earth billions of years ago. Which observation would best support this suggestion?  
 (A) The rocks of the Moon are older than Earth rocks. (B) The Earth has free standing water, but the Moon does not. (C) The Earth and the Moon are gravitationally locked together. (D) The chemical composition of Moon rocks is similar to Earth rocks.
D

Solids, liquids, and gases are all different states of which of the following?  
 (A) mass (B) matter (C) weight (D) volume
B

Noah visited a park that had many oak trees. Which best describes the role of an oak tree in its ecosystem?  
 (A) Oak trees can live for a long time. (B) Oak trees have leaves that change colors. (C) Oak trees have strong branches and trunks. (D) Oak trees are a source of food and shelter for animals.

D