A:63g/mol
B:122g/mol
C:126g/mol
D:163g/mol
解下列一元一次不等式组:
瓦斯已成为导致煤矿特大恶性事故的“头号杀手”.瓦斯存在于煤层及周围岩层中,是井下有害气体的总称.
(1)瓦斯属于____ (选填“纯净物”或“混合物”).瓦斯的主要成分是甲烷,瓦斯爆炸会产生高温、高压和冲击波,并放出有毒气体.甲烷在空气中燃烧的化学方程式是:____ .
(2)为了防止煤矿爆炸,应采取的措施是:____.
My name is Anna.I have my lunch at school from Monday to Friday.I like my school lunch.On Mondays we have hamburgers and milk.On Tuesdays and Fridays we have tomato noodles and beef.I like Wednesdays because we often have sandwiches on Wednesdays.On Thursdays we often have noodles.
根据短文内容判断句子的正误。
欣欣同学的学习生活丰富多彩,下列情景体现了欣欣同学学习生活的片断。回答问题。