光明商店上午卖出a台冰箱，下午卖出b台冰箱，这天一共卖了ab台．______．

53. I’m afraid I can’t keep _______ my classmates as I’ve missed so many lessons. I have to ask my teacher for help.

A．up

B．with

C．up with

D．on with

有一项科学实验，设置两个实验组，第一组实验者摄取大量维生素C，第二组实验者没有摄取维生素C。结果发现，摄取大量维生素C的人比没有摄取维生素C的人对于流感有更强的抵抗力。这一实验表明，维生素C会影响人对流感的抵抗力。
以下哪项为真，最能支持上述结论( )

A．两组被实验者的人数相等
B．两组被实验者对流感的抵抗力在实验前是相当的
C．第一组被实验者摄取的维生素C大大超出日常生活摄取的量
D．这项研究是在流感高发季节做出的

根据作品的表现形式不同，著作权法保护的作品主要有( )。
①文字作品；②口述作品；③音乐、戏剧、曲艺、舞蹈、杂技艺术作品；④美术、建筑作品；⑤摄影作品

A．②④⑤
B．①③⑤
C．②③④
D．①②③④⑤

I’ve recently turned fifty, which is young for a tree, midlife for an elephant, and ancient for a sportsman. Fifty is a nice number for the states in the US or for a national speed limit but it is not a number that I was prepared to have hung on me. Fifty is supposed to be my father’s age, but now I am stuck with this number and everything it means.
A few days ago, a friend tried to cheer me up by saying, "Fifty is what forty used to be. "He had made an inspirational point: Am I over the hill People keep telling me that the hill has been moved, and I keep telling them that the high-jump bar has dropped from the six feet I once easily cleared to the four feet that is impossible for me now.
"Your are not getting older, you are getting better," says Dr. Joyce Brothers. This, however, is the kind of doctor who inspires a second opinion.
And so, as I approach the day when I cannot even jump over the tennis net, I am moved to share some thoughts on aging with you. I am moved to show how aging feels to me physically and mentally. Getting older, of course, is obviously a better change than the one that brings you eulogies (颂词，悼词). In fact, a poet named Robert Browning considered it the best change of all:
Grow old along with me!
The best is yet to me.
Whether or not Browning was right, most of my first fifty years have been golden ones, so I will settle for what is ahead being as good as what has gone by. I find myself moving toward what is ahead with a curious blend (混合) of both fighting and accepting my aging, hoping that the philosopher(哲学家) was right when he said, "Old is always fifteen years from now. \

When the author turned fifty, people around him ______.

A．tried to comfort him

B．got inspiration with him

C．were more friendly with him

D．found him more talkative

网络等级为A时，采用（）保障客户业务不中断。