TASK DEFINITION: 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'.
PROBLEM: Question: *** *** *** *** *** conductor *** electricity?  (A) metal fork (B) rubber boot (C) plastic spoon (D) wooden bat.

SOLUTION: A.

PROBLEM: Question: Tobias *** his *** on a road for a *** *** ***. On average, he *** a *** *** *** *** *** *** during this ***. Which of the following was his *** *** for this *** *** ***?  (A) 10 km/hr (B) 15 km/hr (C) 20 km/hr (D) 25 km/h.

SOLUTION: E.

PROBLEM: Question: Which example best shows structures that make up the digestive system in the human body?  (A) heart, blood, vessels (B) nose, trachea, lungs (C) brain, spinal cord, nerves (D) esophagus, stomach, intestine.

SOLUTION:
D.