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]: During which phase of meiosis does the separation of homologous chromosomes occur?  
 (A) prophase (B) anaphase (C) metaphase (D) telophase
[EX A]: B

[EX Q]: An astronomer observes that a planet rotates faster after a meteorite impact. Which is the most likely effect of this increase in rotation?  
 (A) Planetary density will decrease. (B) Planetary years will become longer. (C) Planetary days will become shorter. (D) Planetary gravity will become stronger.
[EX A]: C

[EX Q]: A student is creating a model of a stream in a forested mountain watershed. Which of these features might be included in the model to show how the stream could overload with sediment?  
 (A) a cabin near the stream (B) rocks in the middle of the stream (C) acres of cleared forest above the stream (D) grasses growing along the banks of the stream
[EX A]:
C