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.

What circuit does not allow an electrical current to flow through it?  
 (A) closed (B) open (C) parallel (D) series
B

The body of a fish is covered by scales for  
 (A) decoration. (B) protection. (C) coloration. (D) reproduction.
B

How should a line graph be used to display distance and time data for a moving object?  
 (A) The y-axis should be labeled as time, which is the dependent variable. (B) The y-axis should be labeled as distance, which is the independent variable. (C) The x-axis should be labeled as distance, which is the dependent variable. (D) The x-axis should be labeled as time, which is the independent variable.

D