可以把金刚石、石墨、氧气归为一类物质，下列物质中与它们属于同_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

可以把金刚石、石墨、氧气归为一类物质，下列物质中与它们属于同一类的是（　　）

A．硫粉

B．一氧化碳

C．食盐

D．碳酸钙

答案

金刚石、石墨、氧气等物质都是由一种元素组成的纯净物，属于单质．

A、硫是由一种元素组成的纯净物，属于单质．故选项正确；

B、一氧化碳是由不同种元素组成的纯净物，属于化合物．故选项错误；

C、食盐是由不同种元素组成的纯净物，属于化合物．故选项错误；

D、碳酸钙是由不同种元素组成的纯净物，属于化合物．故选项错误．

故选A．

单项选择题

瞳孔直径大小的变化（）。

A.受副交感神经调节

B.受交感神经调节

C.两者都是

D.两者都无

完形填空

阅读下面短文，从短文后各题所给的四个选项中，选出可以填入空白处的最佳选项。
During my second year of college I had to look for another place to live in. One Sunday after church the pastor(牧师)   36   me to stay in his daughter’s room because she was studying abroad for one year.
To be honest, I really didn’t want to stay with the pastor’s family.   37   then he old me how much rent would be—a very   38__ figure that included one home-cooked meal a day. I thought about it and    39   to move in.
At the end of the term I had planned to make   40   living arrangements, since the daughter was to   41   home. But they suggested I   42   a room with their son. By this time I seemed to have been adopted（收养）into their 43  -- her people became my people. I   44   accepted the offer.
As I emptied the daughter’s bedroom, I thought it might be   45   to have a little sister. But when I later met her, I   46   that this idea of looking after her might be more interesting than I first   47   .
We finally fell in love, married, and have been   48   one another for many years. There have been times that life turned out to be   49   than either of us could have known. But we have always been able to go   50 _ largely because we knew that somebody deeply cared.
It isn’t about marriage—it’s about   51 _ . It’s about mothers and fathers, sisters and brothers and special friends who are as   52 _ as family. It’s about anybody who can say, “I’ll be   53   -- you can count on me. I’ll try to look after you and   54   I will need you to look after me.”
Is there somebody you can   55 ? And is someone counting on you? We travel the path of life best when there is someone to look after, and when someone is looking after us.

A．watching over

B．taking over

C．looking after

D．looking for

B．more challenging

D．more interesting

C．take care of

D．watch out for