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.

What determines how long the Moon takes to complete one cycle of phases?  
 (A) the period of rotation of the Moon around its axis (B) the period of revolution of the Moon around Earth (C) the period of rotation of Earth around its axis (D) the period of revolution of Earth around the Sun
B

The fusion reaction that fuels the Sun converts hydrogen into  
 (A) carbon. (B) iron. (C) neon. (D) helium.
D

The ichthyornis was a type of bird that lived over 65 million years ago. It lived near the sea and hunted for fish over the water. Fossils have been found in Kansas, many miles from the present-day ocean. Which cause of extinction is most likely to be found in the fossil record along with ichthyornis fossils?  
 (A) changes in the environment (B) diseases causing illness (C) changes in the weather (D) predator animals

A