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: *** *** *** *** *** *** *** *** ***?  (A) food and electricity (B) air, food, and shelter (C) water, food, and clothes (D) food, water, and ai.

SOLUTION: E.

PROBLEM: Question: *** *** *** *** activities *** *** forest *** *** positive effect *** *** ecosystem?  (A) Clearing the land to build new homes (B) Planting new trees where old ones were cut down (C) Building a new highway through the area (D) Cutting down trees to make farmlan.

SOLUTION: B.

PROBLEM: Question: Fourth graders are planning a roller-skate race. Which surface would be the best for this race?  (A) gravel (B) sand (C) blacktop (D) grass.

SOLUTION:
C.