[单选题] 天然气为无色无味的易燃气体,其83%~99%的成分为()。天然气液态相对密度(水=1)约为0.45,由液态变为气态体积扩大600倍,爆炸极限为5%~14%。遇火源、热源有着火爆炸危险,与氯气、次氯酸、液氧等强氧化剂接触剧烈反应。吸入高浓度的天然气能造成人窒息死亡。( ) A. 甲烷 B. 乙烷 C. 丙烷 D. 丁烷
A. All Olympic athletes are only winners, not heroes. B. Some Olympic athletes are only winners, not heroes. C. Some heroes are Olympic winners. D. All of the Olympic champions are both heroes and winners. 参考答案:D