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.

[EX Q]: Which organ in a frog has a function similar to the function of lungs in a bird?
(A) kidney (B) skin (C) liver (D) heart
[EX A]: B

[EX Q]: In a lab experiment, students are testing the identity of an unknown powder. Which method is most appropriate to move the powder to a balance?
(A) sweep with a brush onto transfer paper (B) scoop with lab spatula onto transfer paper (C) pinch with fingers and lift onto transfer paper (D) pour from bottle onto transfer paper
[EX A]: B

[EX Q]: A container tips over and liquid spills on the work surface during a laboratory exercise. What should the student do first?
(A) notify the teacher (B) wipe up the spill (C) tell a classmate (D) call the janitor
[EX A]:
A