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.

[Q]: Joanne's science teacher cautioned the class to be skeptical when learning about new scientific discoveries. Why is it important to be skeptical about new discoveries in science?  
 (A) because many scientific discoveries are not based on facts (B) because most scientific discoveries have no scientific value (C) because most scientists make errors when formulating scientific discoveries (D) because all scientific discoveries must be examined critically before they can be accepted
[A]: D


[Q]: Rhinoceroses and horses are related. They have very similar digestive systems and an odd number of toes on their feet. Horses have one toe, and rhinoceroses have three. These facts best support which claim?  
 (A) Horses and rhinoceroses share a common ancestor. (B) Horses and rhinoceroses are genetically identical. (C) Horses are the ancestors of modern rhinoceroses. (D) Horses have descended from modern rhinoceroses.
[A]: A


[Q]: In one of the steps of the carbon cycle, a person exhales a molecule of carbon dioxide (CO2) into the atmosphere. Which of the following is most likely to happen next to the atom of carbon in this molecule?  
 (A) It may be used as part of a sugar in a plant. (B) It may become part of a protein in an animal. (C) It may be consumed as a fossil fuel is burned. (D) It may be decomposed into carbon and oxygen by a bacterium.
[A]:
A