TASK DEFINITION: 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.
PROBLEM: Black fur is dominant to white fur in guinea pigs. If two black guinea pigs (Bb) are crossed, what color will the fur of their offspring be?  
 (A) 100% black (B) 100% white (C) 50% black, 50% white (D) 75% black, 25% white

SOLUTION: D

PROBLEM: A flowing stream contains water at 18°C. Cans of soft drinks at 28°C are lowered into the stream. Which of the following will most likely occur?  
 (A) The soft drink cans will absorb cold energy from the stream's water. (B) The cans will cool until their temperature is the same as the stream's. (C) The temperature of the soft drinks will not change since the cans are sealed. (D) The temperature of the cans will decrease to freezing as long as the stream is flowing.

SOLUTION: B

PROBLEM: Which source of electricity would harm the environment the least?  
 (A) solar power (B) diesel generator (C) hydroelectric dams (D) power lines

SOLUTION:
A