Answer:
B. more difficult when your close friends smoke.
Explanation:
Especially when one is younger and/or has been with your friends in a long term, it may be "more" pressuring to do things with your long-time close friend, even if it is detrimental to your health. B, is the best answer choice for this question.
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The answer is C muscular system
Answer is in a photo. I can only upload it to a file hosting service. link below!

Join a club that you might be interested because your focus would just be on what you like to do in that free time. Plus you could tell everybody what they need to do since you already know how to do it.