《祭侄文稿》是我国唐代著名书法家______的行书作品，被人誉为“天下第二行书”A．

In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.
The key to SNMP (76) is its simplicity. It has a small command set that does a good job of collecting information from (77) any network device. In a SNMP environment, (78) of the work is handled by the network management system. Devices that are being managed are not (79) with processing (80) that might affect their performance.

A．popularity

B．function

C．efficiency

D．power

两个斜均光滑，用力F₁、F₂别沿两个面将同一物体匀速拉到斜面的顶部，做的功分别为W₁、W₂，则下列关系中正确的是（　　）

A．F₁=F₂ 　W₁=W₂

B．F₁＞F₂ 　W₁=W₂

C．F₁＜F₂ 　W₁=W₂

D．F₁＞F₂ 　W₁＞W₂

高速公路上的标志牌常用“回光返照膜”制成，夜间行车时，它能将车灯照射出去的光逆向返回，标志牌上的字特别醒目．这种“回光返照膜”是用球体反射原件制成的．如图所示，反光膜内均匀分布着直径为10 μm的细玻璃珠，所用玻璃的折射率为，为使入射的车灯光线经玻璃的折射、反射、再折射后恰好和入射光线平行，那么第一次入射的入射角是（  ）

A．60°

B．45°

C．30°

D．15°

各种测向机都有共同的结构，包括一套天线阵、一部接收机和一部测向处理器。