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.

[Q]: During a walk in the woods, Mandy finds a plant structure that had fallen onto the trail. Mandy can tell the object contained seeds, and thinks it came from a flowering plant instead of a conifer. How can she determine if the object came from a flowering plant?  
 (A) by looking for seed coats on the seeds (B) by looking for wing-like structures on the seeds (C) by looking for fruit tissue around the seeds (D) by looking for young sporophytes inside the seeds
[A]: C


[Q]: 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.
[A]: C


[Q]: As wave frequency is increased, wave energy  
 (A) stays constant. (B) is unaffected. (C) increases. (D) decreases.
[A]:
C