问题 选择题

下列符号中,既可表示一种物质,也可表示一种元素,还可以表示一种这种元素的一个原子的是(  )

A.H2

B.2H

C.H

D.He

答案

元素符号能表示一种元素,还能表示该元素的一个原子;化学式能表示一种物质,当元素符号又是化学式时,就同时具备了上述三层意义.

A、该符号是氢气的化学式,不是元素符号,故选项不符合题意.

B、该符号表示两个氢原子,不是元素符号,故选项不符合题意.

C、H属于非金属元素,可表示氢元素,表示一个氢原子,但不能表示一种物质,故选项不符合题意.

D、He属于稀有气体元素,可表示氦元素,表示一个氦原子,还能表示氦气这一纯净物,故选项符合题意.

故选D.

阅读理解

When I walked into the house after school, the first thing I noticed was a box with items I recognized from my dad’s office.

“What are you doing home already?” I asked casually.

“Andrew, I was laid off today.” he answered quietly.

I was sure he was joking. “No, you weren’t. Why are you really home?”

Then I noticed his seriousness and realized he was telling the truth. My father has always been a hard worker and prided himself on his career. Providing for our family has been his joy, and I guess I had taken his work for granted.

My father’s unemployment created many changes in our lives. For starters, he was home all the time, which meant my bed had to be made, my room cleaned up, and my homework done right after school. I would come home every day to find him at the computer searching for jobs. I began to notice how down he seemed, and how losing his job had affected his self-esteem, though he tried to be optimistic. For the first time, I saw my dad as vulnerable. He asked my brother and me to spend less. I gave up my allowance, which even though it wasn’t much, felt like the right thing to do. I also found a part-time job.

After several difficult months of searching, my dad decided to go in a totally different direction. He explained that he never wanted to be laid off again, so he was going to start his own business. Day by day, I watched him build it, and I admired how much time and energy he expended.

One evening I asked if he needed help.

“Only if it doesn't interfere with school,” he said.

I showed up at his office the next afternoon, and most afternoons after that for two months. I always knew he was a hard worker, but watching him in action really impacted me. Although this was one of the worst experiences for our family, it taught me a lot about dealing with adversity. Now I know that through creative problem-solving, I can always find Plan B, ask for help, and take risks. What I have learned from my dad’s understanding of business and his work ethic are two of the most important lessons I will ever learn, and will be my foundations for success.

1. The author’s father stayed at home because ________.

A. he had to help with the author’s lesson

B. he had been unemployed by his company

C. heavy housework was waiting for him to do

D. he wanted the author know the truth?

2. What made the author know the truth?

A. The box from his dad’s office                         B. His father’s words

C. His father’s expression                                          D. Being informed by his family

3. The author’s attitude toward his father’s former job was ________.

A. unconcerned                      B. sympathy                 C. doubt                D. tolerance

4. By saying “Only if it doesn't interfere with school”, the author’s father seemed ________.

A. to refuse the author’s advice on the new business

B. to show his discontent with the author’s schoolwork

C. to have said yes to the author’s offer of help

D. to be looking forward to the author’s good behavior at school

5. It can be inferred from the text that ________.

A. the author’s father was more optimistic to stay at home

B. the author couldn’t put up with his dad’s own business

C. the author’s father offered little allowance to the author

D. the author benefited from his father on how to deal with adversity

多项选择题