问题
选择题
化学与科技、生产、生活密切相关。下列说法正确的是（ ）
A．气象环境报告中的“PM2.5”是对一种新分子的描述
B．高铁车厢采用的铝合金材料强度大、质量轻，不与氧气反应
C．“玉兔号”月球车太阳能电池帆板的材料是二氧化硅
D．地沟油的主要成分是油脂，其组成与汽油、煤油不相同
答案
答案：D
题目分析：A、“PM2.5”是指空气中直径小于或等于2.5微米固体颗粒或液滴的总称，是混合物，不是新分子，错误；B、铝在空气中与氧气反应生成一层致密的氧化物薄膜，阻止了反应的进行，错误；C、太阳能电池的材料是晶体硅，不是二氧化硅，错误；D、地沟油的作用成分是油脂，属于酯类，而汽油、煤油的主要成分是烃，二者的成分不同，正确，答案选D。
o applied the minimum living standard protection (最低生活保障) system for the aged who are unable to work and receive no supports. Now, China is bringing the aging problem into the work of sustainable (持续的) development according to China’s conditions, to build and develop a social security system for old people, set up a system combined with the state, collectives (集体) and families to solve the problem of “the elderly should be provided for”. The life of China’s old people is more colorful along with the fast and sound economic development of the country.
sty for knowledge. Strong and healthy old people can be seen everywhere of the country. They learn new knowledge, surf the Internet, practice handwriting and drawing, and take part in fashion shows, exercises and entertainments. Their active and sound living attitude encourages the youth around and they are in fact an important role in ensuring a stable and peaceful society.