In this subtask, you will answer a simple science question. Please indicate the correct answer. If you're not sure about the answer, choose the last option "I don't know". Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D', 'E'. The "A"-"D" responses correspond to the answer options mentioned in the input. There is a 5th option "E" which should be used for questions for which you're not sure about the answer (e.g., when the questions do not provide enough information to answer).

Ex Input:
Question: A student wants to find out how many different kinds of birds are found in a park. In addition to a bird identification book, the student should use  (A) binoculars (B) goggles (C) a microscope (D) a hand len?

Ex Output:
A.


Ex Input:
Question: A student spills a cup of water onto a table. What property of the water has changed?  (A) chemical composition (B) volume (C) color (D) mas?

Ex Output:
B.


Ex Input:
Question: On a hiking trip to Big Bend National Park, a hiker found a sedimentary rock. The hiker would like to find the mass of the rock. Which tool would be used to find the mass of the rock?  (A) Incline plane (B) Balance (C) Meter stick (D) Graduated cylinde?

Ex Output:

B.