Choices:
[1]. clean air;
[2]. fresh scent;
[3]. Toxicity;
[4]. Pollution;
[5]. negative;
[6]. lung cancer;
[7]. healthy lungs;
[8]. Dehydration;
Given those answer options, answer the question: Fact 1: Lung cancer is most often caused by exposure to tobacco smoke. Fact 2: Secondhand smoke is also known as Environmental Tobacco Smoke. Given the two facts above, what can be caused by secondhand smoke?
A:
[6].