instruction:
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.
question:
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
answer:
B


question:
The vampire finches in the Galápagos Islands peck at another species of bird, the blue-footed booby, until the finches make a wound. Then, the finches drink the booby's blood. Scientists think that many generations ago finches used to peck bugs off the booby, and the behavior evolved to what it is today. Which statement best describes the birds' relationship generations ago and the relationship today?  
 (A) The old relationship was parasitic. The new relationship is mutualistic. (B) The old relationship was mutualistic. The new relationship is parasitic. (C) Both relationships are parasitic. (D) Both relationships are mutualistic.
answer:
B


question:
Nonaggressive birds called purple martins nest each spring to lay eggs. Starlings are aggressive birds that will eat the purple martin's eggs and nestlings. Which will most likely be the effect on both populations after a starling invasion?  
 (A) Purple martins will increase and starlings will decrease. (B) Purple martins will increase and starlings will increase. (C) Purple martins will decrease and starlings will decrease. (D) Purple martins will decrease and starlings will increase.
answer:

D