TASK DEFINITION: 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.
PROBLEM: Which part of an atom is involved in chemical reactions?
(A) nucleus and its particles (B) negatively-charged particles (C) neutrally-charged particles (D) positively-charged particles

SOLUTION: B

PROBLEM: Similar types of cells form tissues. What is the next level of complexity formed from the grouping of tissues?
(A) organs (B) organelles (C) organisms (D) organ systems

SOLUTION: A

PROBLEM: How are bacterial cells and human cells alike?
(A) They allow oxygen through the cell wall. (B) They allow carbon dioxide through the cell wall. (C) They allow nutrients through the cell membrane. (D) They allow nutrients through the nuclear membrane.

SOLUTION:
C