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.

Campers shouted toward a canyon wall. What characteristic of sound best explains why the campers heard an echo?  
 (A) Sound waves traveled slowly down the canyon. (B) Sound waves were absorbed by the canyon wall. (C) Sound waves reflected off the canyon wall. (D) Sound waves were refracted around the canyon.
C

Which situation is the best example of an inherited trait?  
 (A) a boy playing with a ball (B) a bird building a nest (C) a horse pulling a wagon (D) a dog sitting on command
B

The European starling entered North America in the late 1800s. It proved very successful and was able to spread throughout the United States by 1955. The survival and rapid reproduction of starlings most likely limited the population size of which organisms within its habitats?  
 (A) its decomposers (B) its competitors (C) its mutualists (D) its predators

B