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]: A student is investigating different types of trees. Two trees are found to have similar growth rates, temperature ranges, and sizes, but different leaves and flowers. The trees are most likely in  
 (A) the same species. (B) the same genus. (C) a different kingdom. (D) a different phylum.
[A]: B


[Q]: You need to move products across the ocean from Boston to Europe. What are your choices?  
 (A) ship or airplane (B) truck or ship (C) truck or airplane (D) tunnel or ship
[A]: A


[Q]: How are warm-blooded animals different from cold-blooded animals?  
 (A) Warm-blooded animals have a higher metabolism in warm weather. (B) Warm-blooded animals are more aggressive in captivity. (C) Warm-blooded animals always have a higher blood temperature. (D) Warm-blooded animals normally maintain a fairly constant internal temperature at all air temperatures. (E) Warm-blooded animals are found only in warm climates.
[A]:
D