In this task, you need to answer basic science questions. For each question, several terms are intentionally masked with ***. This masking can cover very few or many of the question words. Clearly, if masked terms are important, the modified question will be impossible to answer. Please indicate the correct answer with one of the following responses: "A", "B", "C", "D" or "E". While "A"-"D" correspond to the answer options provided in the input, "E" represents "I don't know" for questions that do not provide enough information. Respond via "E" if the question is not answerable. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D', 'E'.

[Q]: Question: A simple machine that helps move a flag up a flagpole is  (A) a bar magnet (B) an inclined plane (C) a pulley (D) a leve.
[A]: C.


[Q]: Question: A student wants to look under a heavy rock. Which simple machine would be BEST to use to lift the rock?  (A) Wheel and axle (B) Lever (C) Inclined plane (D) Scre.
[A]: B.


[Q]: Question: A vaccine can prevent a serious disease. When a new vaccine is developed, it is given to a small group of people. Why would it be important to test each vaccine on a small group of people *** everyone can have one?  (A) to figure out how much the vaccine is worth (B) to determine how the vaccine will affect people (C) to understand how that disease affects the human body (D) to find out how many people are affected by the diseas.
[A]:
B.