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.

Ella waves good-bye from the bus. What body system pulls on bones to let Ella wave her arm?  
 (A) muscular system (B) nervous system (C) digestive system (D) circulatory system
A

Typically, sedimentary rocks are formed  
 (A) only in erupting volcanoes. (B) only under great pressure and high temperatures. (C) below Earth's surface as magma cools and crystallizes. (D) from materials that settle.
D

The oldest Moon rocks have been dated to a time shortly after the estimated date of the formation of our solar system. Approximately how old are these Moon rocks?  
 (A) 6.4 billion years (B) 4.5 billion years (C) 2.8 billion years (D) 1.7 billion years

B