下列活动不需要进行会计核算的有______。 A．订立经济合同 B．确定企业投资方案

设函数f（x）定义域为R，当x＞0时，f（x）＞1，且对任意x，y∈R，有f（x+y）=f（x）•f（y）．

（1）证明：f（0）=1；

（2）证明：f（x）在R上是增函数；

（3）设集合A={（x，y）|f（x²）•f（y²）＜f（1）}，B={（x，y）|f（x+y+c）=1，c∈R}，若A∩B=φ，求c的取值范围．

阅读理解

     Marriages improve after children grow up and move out, according to an academic study, which

suggests an "empty nest" is not always a bad thing.

     Popular wisdom has it that parents' relationships may suffer once their young fly the coop, because

they feel they have lost their purpose in life.However, a new study by researchers at the University of

California,  Berkeley, has found that many couples actually feel happier when their children leave home

because they are able to enjoy spending time together.

     In total,123 American mothers born in the 1930s were tracked for 18 years and asked to rate their

satisfaction levels shortly after marrying, when they were bringing up babies, once their children reached

their teenage years and finally at age 61, when almost all had "empty nests".

     Although not all said they were happier in general, most claimed their marriages had improved since

their children had left home.Researchers believe this is not just because the spouses were spending more

time together, but because they were able to enjoy each other's company more.

     One of the participants in the study, which is published in the journal Psychological Science, said:"

Once the kids grow up...there's some of that stress removed...that responsibility removed, so things are

a little more relaxed."

     Psychologist Sara Gorchoff, who carried out the investigation, said:"The takehome message for

couples with young children is 'hang in there'. " Her coauthor Oliver John added:"Don't wait until your

kids leave home to schedule quality time with your partner."

      However, Dr Dorothy Rowe, from the British Psychological Society, said the effects of living in an

"empty nest" will depend on the parents' relationship with their children."If you're just waiting for them

to leave home so you can get on with your life, then of course you'll be pleased to see them go, " she

said, "But if you've built your life around your children you'll be terribly lonely.For some parents, their

world falls apart when their children leave."

1. It is commonly believed that________.

A. marriages improve after children leave home

B. an "empty nest" is always a happy thing

C. parents' relationships may suffer once their young grow up and move out

D. parents will be pleased after their children leave home

2. When did many couples feel happier according to the study?

A. At age 61, when almost all had "empty nests".

B. Shortly after marrying.

C. Once their children reached their teenage years.

D. When they were bringing up babies.

3. Marriages improve after children fly the coop not because______.

A. many couples are able to spend time together

B. many couples are able to enjoy each other's company

C. things are a little more relaxed

D. many couples needn't work at all

4. The author of the passage tends to agree that________.

A. parents should build their life around their kids

B. parents should schedule quality time with each other before kids leave home

C. parents' relationship with their kids has no effect on marriages at all

D. parents should be pleased to see their kids leave home

以下叙述中正确的是

A．C程序的基本组成单位是语句

B．C程序中的每一行只能写一条语句

C．简单C语句必须以分号结束

D．C语句必须在一行内写完

热饮塑料杯盖上的三角形符号中标着“6”，下列哪个说法是正确的？（）

A.杯盖的直径是6厘米

B.聚苯乙烯材料不能在微波炉中加热

C.聚氯乙烯材料能在微波炉中加热

D.只耐60℃温度

被跨越的低压线路或弱电线路需要开断时，应事先征得有关单位的同意。开断低压线路应遵守停电作业的有关规定。开断时应有防止电杆（）的措施。

A.倾倒

B.断裂

C.感应电

D.移动