任何一个具有两个属性的关系A．可能属于1NF B．可能属于2NF C_爱下问搜题

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问题单项选择题

任何一个具有两个属性的关系

A．可能属于1NF

B．可能属于2NF

C．可能属于3NF

D．一定属于3NF

答案

参考答案：D

解析：具有两个属性的关系，只可能有两种情况：一种情况是其中一个属性为主属性，另一个为非主属性，这样就不存在非主属性对码的部分函数依赖和传递函数依赖，属于3NF；另一种情况是两个属性均为主属性，没有非主属性，当然根本谈不到非主属性对码的部分函数依赖和传递函数依赖，属于3NF。所以任何一个具有两个属性的关系，一定属于3NF，从而也一定属于1NF和2NF。可见只有选项D)是正确的。

完形填空

I was shopping at my local supermarket, as I normally have for years. One particular day, I had done about 2 weeks worth of shopping and        toward the register to pay for what I bought. After the cashier(收银员) had scanned my items and I had bagged them up, she stated（说） that the       was $150.
I         into my back right pocket to take the money to pay and noticed that there was no money there. I started to get       . I knew my purse was in the car and I was sure I had put the        in my back right pocket. I looked at the cashier with wet eyes and a       look not knowing what to do. There were people behind me on the line. She told me to speak with the courtesy counter (爱心柜台).  I        and said, “Really? It's        , no one would hand that in!”  But she        me to. “You never know…” she said.
I decided that there was no        in checking so I walked up to a woman behind the counter and said “I have to ask, did anyone        cash by any chance?” She asked “How much?” My face then       .  “$200 in the form of one hundred dollar bills.” I replied. She said, “       , yes, someone did!” I was so       ! “Who? I want to thank her.” She pointed to a young girl about 10 years old and said, “She did.”
I walked over to the mom and hugged her. She said, “It wasn't me, it was my       ” . I said “I know, I wanted to thank you both,       she found it ... it's because of you that I got this back.” I was so happy. I was almost in tears.
The next day at work, a person in another department        me tickets to the circus（马戏团). He handed me 5 tickets. Almost        that young girl’s face popped (突然出现) in my head. After work I went back to the supermarket and stopped at the courtesy counter and asked if she had any idea who that woman was. She smiled and said, “Yes, She is a friend of mine”.  Then I asked her to do me a favor and pass along these 5 tickets to her.
She told me that the family of the little girl who found my money were not rich so they would really        this. She also said that they had 3 children, so five was the        number of tickets!

C．discouraged

D．Unfortunately

C．immediately

单项选择题

关于血涂片制备的描述，错误的是

A．血滴越大血膜越厚

B．角度越大血膜越薄

C．推片速度越快血膜越厚

D．载玻片不清洁血膜可出现气泡

E．推片用力不均匀，血膜呈搓板状