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 example best shows structures that make up the digestive system in the human body?
(A) heart, blood, vessels (B) nose, trachea, lungs (C) brain, spinal cord, nerves (D) esophagus, stomach, intestines
[EX A]: D

[EX Q]: Which of the following has the least momentum?
(A) a 0.5 kg mass with a 1000 m/s velocity (B) a 1 kg mass with a 100 m/s velocity (C) a 10 kg mass with an 11 m/s velocity (D) a 100 kg mass with a 2 m/s velocity
[EX A]: B

[EX Q]: In which way is any single observation of wind speed best described?
(A) It is an indication of a future weather condition. (B) It is an indication of the amount of humidity. (C) It is an indication of weather at a specific time. (D) It is an indication of the existing climate.
[EX A]:
C