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.

[Q]: The planets in the solar system revolve around the Sun because the Sun is  
 (A) made of hydrogen and helium. (B) older than other objects in the solar system. (C) the source of most heat and light energy. (D) the strongest source of gravity in the solar system.
[A]: D


[Q]: Two flowers are both roses. One rose is larger and has more fragrance than the other rose. What advantage will one of the roses most likely gain because of this difference?  
 (A) The larger rose will have fewer petals than the smaller rose. (B) The larger rose will more easily attract bees than the smaller rose. (C) The smaller rose will have more pollen than the larger rose. (D) The smaller rose will grow faster than the larger rose.
[A]: B


[Q]: Jeremy walked at an average rate of speed of 3 kilometers per hour (km/h). How far had Jeremy walked in 30 minutes?  
 (A) 0.1 km (B) 1.5 km (C) 10 km (D) 90 km
[A]:
B