哲学是对生活本质的认知，理性的认识，艺术家站在哲学家的肩膀上，其艺术作品能够反映出生

下列说法中不正确的是(　　)

A．人走路时，会受到静摩擦力作用

B．武警战士双手握住竖立的竹竿匀速上攀时，所受的摩擦力的方向是向下的

C．将酒瓶竖直用手握住停留在空中，当再增大手的用力，酒瓶受的摩擦力不变

D．在结冰的水平路面上撒些细土，人走上去不易滑倒，是因为此时人与路面间的最大静摩擦力增大了

具有自锁性能的蜗杆传动，其效率为（）。

A．(70～80)%

B．高于50%

C．低于50%

阅读理解。

     These are instructions for making invisible ink using baking soda.

     Difficulty: Easy

     Time required: A few minutes

     What you need:

     Baking soda

     Paper

     Water

     Light bulb

      Paintbrush

     Measuring cup

     Purple grape juice

     Here's how:

     There are at least two methods of using baking soda as invisible ink. Mix equal amounts of water and

baking soda.

     Use a paintbrush to write a message onto white paper, using the baking soda solution (溶液) as "ink".

     Allow the ink to dry.

     One way to read the message is to hold the paper up to a heat source, such as a light bulb. The baking

soda will cause the writing in the paper to turn brown.

     The second way to read the message is to paint over the paper with purple grape juice. The message will

appear in a different color. Tips:

     If you are using the heating method, avoid igniting (点燃) the paper.

     Baking soda and grape juice react with each other in an acid-base (酸碱) reaction, producing a color

change in the paper.

     Grape juice concentrate (浓缩物) results in a more visible color change than regular grape juice.

1. ______ is not needed for making invisible ink.

A. Baking soda

B. Paper

C. Water

D. Ink

2. What's the function of the paintbrush?

A. To draw a picture.

B. To write a message onto the white paper.

C. To allow the"ink" to appear.

D. To help the"ink" dry.

3. Why will the message appear in a different color in the second way to read the massage?

A. Because there is enough grape juice.

B. Because baking soda reacts with grape juice.

C. Because of the use of water.

D. Because of the special paper.

4. From the process, we can know that making invisible ink is ______.

A. very hard

B. not difficult

C. a little difficult

D. not easy

Directions: Read the following passage. Complete the diagram by using the information from the passage.

Write NO MORE THAN THREE WORDS for each answer.

Rest is critical to life and work and a positive attitude towards rest needs to be maintained, for enough rest is significant to our body and mind while a lack of adequate rest, as well as misleading attitudes to rest, will do great harm to our health.

Rest is vital to our ability to function at our best. Recent news stories report that scientists are learning surprising things about the importance of sleep. There is enough evidence suggesting that rest will refresh us, enabling our body and mind to work efficiently. Besides, rest is important for more than that; it is helpful in setting appropriate goals and deciding what goals to attain first. Those who are caught up in extremely busy lives lack the time to think about what they are doing and to make objective decisions, which blocks the maximization of their potential.  

On the contrary, lack of adequate rest damages brain function, so much so that sleep experts have been able to measure drops in IQ in patients who are short of sleep. Other studies have presented a negative effect on body movements in sleep-wanting subjects. It should not, therefore, be a surprise that the California Highway Patrol has stated that sleep-wanting drivers are as great a threat to road safety as are drunk drivers.

However, rest is widely misunderstood by some people. Instead of sleep, they go to pubs and clubs and claim that this kind of entertaining is rest. For example, what they call social drinking or having a smoke with friends. Nowadays, the economy forces people to drink and gamble for the sake of the circles one moves in. This is what fools claim thoughtlessly that it’s restful. The truth is that rest means not using our labor both physically and mentally, even spiritually.

We need to rest correctly and sufficiently; otherwise, tiredness and illness will occur. Without sufficient rest, good work is impossible.Rest is critical; it is not an end in itself.

稳态