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: Nectar is a sweet liquid that some flowering plants produce. A hummingbird drinks nectar from a flower. When a hummingbird drinks nectar, pollen from the flower sticks to the hummingbird's beak. The picture shows a hummingbird drinking nectar from a flower. Which statement explains the role of a hummingbird in the life cycle of a flowering plant?  
 (A) A hummingbird carries food to the plant. (B) A hummingbird helps the plant reproduce. (C) A hummingbird protects the plant from predators. (D) A hummingbird makes the flowers produce nectar.

SOLUTION: B

PROBLEM: Which element makes up most of the air we breathe.  
 (A) carbon (B) nitrogen (C) oxygen (D) argon

SOLUTION: B

PROBLEM: Which physical characteristic of Earth is similar to a physical characteristic of the Moon?  
 (A) its climate (B) its great seas (C) its atmosphere (D) its mountain ranges

SOLUTION:
D