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.

Which activity is an example of a good health habit?  
 (A) riding a bicycle without a helmet (B) smoking cigarettes (C) wearing a hat while in the Sun (D) eating with dirty hands
C

What causes a ship carrying heavy cargo to take more time to come to a stop than an identical ship carrying lighter cargo if both ships are traveling at the same speed?  
 (A) increased friction (B) greater momentum (C) greater acceleration (D) more constant velocity
B

Populations living in one place form a  
 (A) community (B) system (C) habitat (D) species

A