TASK DEFINITION: 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.
PROBLEM: Which of the following is a step in the life cycle of an apple tree?  
 (A) Eggs grow from seedlings. (B) Fruit forms flowers. (C) Seedlings grow from leaves. (D) Fertilized flowers form fruit.

SOLUTION: D

PROBLEM: Some plants produce fruit such as apples. What is one function of a fruit?  
 (A) to protect seeds (B) to produce food for seeds (C) to stop seeds from dispersing (D) to store water for seed germination

SOLUTION: A

PROBLEM: The speed of a sound wave varies as it travels through different substances. Which factor will most affect the speed of a sound wave?  
 (A) the frequency of the wave (B) the wavelength of the wave (C) the source that created the sound (D) the distance between molecules in the medium

SOLUTION:
D