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.

Which of these tools is best for recording observations outdoors?  
 (A) a ruler (B) a graph (C) a notebook (D) a calculator
C

Which step will most likely ensure that the results of an investigation are valid?  
 (A) using a computer to graph results (B) verifying that results match the original hypothesis (C) comparing the results with those of other scientists (D) eliminating any results that appear to be abnormal
C

A negatively-charged ion has  
 (A) a heavier nucleus. (B) a greater atomic mass. (C) more electrons than protons. (D) more electrons than neutrons.

C