You are given a science question (easy-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]: Cell division is necessary for an organism to  
 (A) obtain nutrients. (B) grow and reproduce. (C) make proteins. (D) conserve matter and energy.
[EX A]: B

[EX Q]: Some scientists believe that the mass extinction of dinosaurs was caused by the impact of a large meteorite on Earth. This impact would have caused a darkening of the sky due to dust blown into the upper atmosphere. This darkening would have reduced the sizes of some ecosystems because of  
 (A) longer seasons. (B) accelerated erosion. (C) reduced photosynthesis. (D) increased number of hurricanes.
[EX A]: C

[EX Q]: In the first half of this century, which technology allowed people, for the first time, to work IN the city but live OUTSIDE the city?  
 (A) airplanes (B) automobiles (C) telephones (D) television
[EX A]:
B