设备检修验收合格后方可投入使用。设备检修经施工单位质监部门验收合格后，（）、C类设备

滚动轴承的组成部分？

Garden of small inventions

Visitors of all ages are invited to Port Discovery to see the new exhibit—a garden of small inventions, which features interactive activities and gadgets(小器械，小物件，小玩意) for the environmental protection. The exhibit runs through Sept.4. Fee is $10.75; free for ages younger than two. Contact 410-727-8120 or portdiscovery.org.

Rain-barrel workshop

The Parks and People Foundation presents a workshop on building water-efficient rain barrels for the home between 6pm-8pm on Wednesday at the foundation’s Stieff Silver Building. Cost is $50 and includes the barrel and all materials. Contact 410-448-5663, ext.109.

Pruning(修剪)plants

Visitors can attend a workshop on pruning plants between 9:30am-10am on Tuesday at Ladew Topiary Gardens. Visitors should meet in the Visitors Center at Ladew, Jarrettsville Pike, Monkton. $10; free for Ladew members, and includes admission to the gardens and the nature walk. Contact 410-557-9570 or www.ladewgardens.com.

Landscape exhibit

Photographs, paintings and drawings will be shown at Landscape and Nature—a view from Maryland, through Sept.9 at the University of Maryland. Opening reception is between 5pm-7:30pm on Tuesday. Contact 301-985-7937 or um.edu/art.

小题1:It will cost a couple with their newly-born baby________ to visit Port Discovery.

A．$ 30

B．$100

C．$21.5

D．nothing小题2:To learn how to make your flowers grow better, you will probably go to __________.

A．Port Discovery

B．Stieff Silver Building

C．Ladew Topiary Gardens

D．the University of Maryland小题3:You will call _______ to get information about learning something about art.

A．410-727-8120

B．410-448-5663

C．410-557-9570

D．301-985-7937小题4:Which activity is offered only on Wednesday according to the ads?

A．Garden of small inventions

B．Rain-barrel workshop

C．Pruning(修剪)plants

D．Landscape exhibit

（14分）如图，可看作质点的小物块放在长木板正中间，已知长木板质量为M=4kg，长度为L=2m，小物块质量为m=1kg，长木板置于光滑水平地面上，两物体皆静止。现在用一大小为F的水平恒力作用于小物块上，发现只有当F超过2.5N时，才能让两物体间产生相对滑动。设两物体间的最大静摩擦力大小等于滑动摩擦力大小，重力加速度g=10m/s²，试求：

（1）小物块和长木板间的动摩擦因数。

（2）若一开始力F就作用在长木板上，且F=12N，则小物块经过多长时间从长木板上掉下？

在一定条件下，将物质的量相同的NO和O₂混和，发生如下反应：2NO＋O₂＝2NO₂，2NO₂N₂O₄，所得混合气体中NO₂的体积百分含量为40%，此时，混合气体的平均分子量为[ ]

A．49.6

B．41.3

C．62

D．31

由上皮组织发生的、缺乏分化状态的肿瘤称（）

A．腺癌

B．单纯癌

C．未分化癌

D．鳞状细胞癌

E．腺鳞癌