数列{an}中,a1=1,an,an+1是方程x2-(2n+1)x+1bn=0的

题型:选择题

问题:

数列{an}中,a1=1,an,an+1是方程x2-(2n+1)x+
1
bn
=0
的两个根,则数列{bn}的前n项和Sn等于(  )
A.
n
2n+1
B.
n
n+1
C.
1
2n+1
D.
1
n+1
考点:数列求和的其他方法(倒序相加,错位相减,裂项相加等)
题型:选择题

历史上某些时期,国家制度发生重大变化,被称为“大变革”。下列叙述中不能称为“大变革”的是(    )

A.商周之际,属国变为封国

B.春秋战国,分封变为郡县

C.三国时代,统一走向分裂

D.清末民初,专制变为共和

题型:选择题

除灰管道运行中应注意哪些事项?

题型:选择题

庆大霉素与羧苄青霉素混合注射

A.协同抗绿脓杆菌作用

B.属于配伍禁忌

C.用于急性心内膜炎

D.用于耐药金黄色葡萄球菌感染

E.以上都不是

题型:选择题

Directions: Complete the following passage by using ONE word that best fits the context.

Thanksgiving Day was near. The first grade teacher gave her class   48  fun assignment --- to draw a picture of something for which they were thankful.

Most of the class would celebrate the holiday with turkey and other traditional goodies of the season. These, the teacher thought, would be the themes of most of her students’ art. And they were. Douglas made a different kind of picture,   49 . When asked to draw a picture of something for which he was thankful, he drew a hand. Nothing else. Just an  50  hand .

His abstract image captured the imagination of his peers. Whose hand could it be? One child guessed it was the hand of a farmer, because farmers raise turkeys.   51  suggested a police officer’s, because the police protect and care   52  people. Still others guessed it was the hand of God, for God feeds us. And so the discussion went --- until the teacher almost forgot the young artist himself.

When the children had gone on to other assignments, she stopped at Douglas’ desk, bent down, and asked him 53  hand it was. The little boy looked away and said, “It’s yours, teacher.”

She recalled the times she had taken his hand and walked with him here or there, as she had the other students. How  54  had she said, “Take my hand, Douglas, we’ll go outside.” Or, "Let me show you how to hold your pencil.” Or, “Let's do this together.” Douglas was most thankful for his teacher's hand. Brushing aside a tear, she went on with her work.

The story speaks of more than thankfulness. It says something about teachers teaching and parents parenting and friends showing friendship, and how much it means to the Douglases of the world. They might not always say thanks,  55  they'll remember the hand that reaches out.

题型:选择题

成人骶管容积为()

A.20~25ml

B.25~30ml

C.30~35ml

D.35~40ml

E.40~45ml

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