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.

A pot is touching the flame of a gas stove, and the substance in the pot is heating up due to the contact. This is an example of which type of energy transfer?  
 (A) radiation (B) convection (C) conduction (D) vaporization
C

In a copper wire, a temperature increase is the result of which of the following?  
 (A) an increase in the size of the copper particles (B) a decrease in the mass of the copper particles (C) an increase in the motion of the copper particles (D) a decrease in the distance between the copper particles
C

Which group on the periodic table contains elements that are the least reactive?  
 (A) group 1 (1A) (B) group 3 (3B) (C) group 16 (6A) (D) group 18 (8A)

D