Across the Deserts

　　The SaharaDesertis the largest desert in the world. It stretches across Africa fromSenegaltoEgypt. TheSaharaDesertis an unfriendly environment. During the day it"s very hot, and at night it’s sometimes very cold. It is also difficult to find water in theSahara.

　　In 2006, Kevin Lin, Ray Zahab, and Charlie Engle decided to do something very difficult. They made the decision to run across the Sahara Desert 4,300 miles (6,920km). It seemed impossible to do, but they wanted to try. The three men liked to test themselves, and this would be a very big test.

　　On the morning of November 2, Kevin, Ray, and Charlie started their trip across theSahara. Every morning they began running at 5:00. At11 a.m. they stopped and rested until 5 p.m. Then they ran again until 9:30 in the evening. Each day they ran about 40 miles (64 km). Every day it was the same thing. They got up and ran. They listened to music on their iPods, and they ran and ran.

　　Kevin, Ray, and Charlie needed to eat a lot of food during their trip. Most people need about 2,000 calories of food each day. Kevin, Ray, and Charlie needed between 6,000 and 9,000 calories every day. That"s a lot of food! They also needed to drink a lot of water.

　　The three men had some problems on their trip, and many times they wanted to quit and go home. It was often very hot (140°F/60°C) during the day, and the heat made them sick. Their legs and feet hurt. Sometimes it was very windy, and they couldn"t see. One time they got lost. But they didn"t quit. After 111 days, Kevin, Ray; and Charlie successfully finished their trip across theSaharaDesert. They hugged each other and put their hands in the water of theRed Sea. Then they ran to a hotel to take a long shower.

　　词汇：

　　Stretch / strɛtʃ / v. 延伸，伸展

　　Calorie / "kælərɪ / n. 卡(路里)，小卡，大卡

　　Quit / kwɪt / v. 停止，放

　　注释：

In the middle of the day: the men usually stopped running.

A:Right B:Wrong C:mentioned

“iu、ui”的声调应该标在（）。

A:“i”上 B:“iu”标在“i”上，“ui”标在“u”上 C:“u”上 D:“iu”标在“u”上，“ui”标在“i”上

若10位A/D芯片工作于5V，当采样结果为0100000000，输入电压Ui为（）

A:1.25V B:2.5V C:0.06255V D:0.3125V

UI

有两个电容器，C1为300V、60μF，C2为200V、30μF，将他们串联后其总的耐压为（）。

A:100V B:200V C:300V D:500V

有C1、C2两个电容器，C1为300V、60µF，C2为200V、30µF，并联后其总的耐压为（）。

A:500V B:300V C:200V D:100V

某电压表的标称范围是－60V～＋300V，其量程是（）

A:360V B:300V C:+300V D:240V

电压比较器如图7-57所示，稳压管的稳定电压Uz=6V，其中正向电压降为0.7V，uR=10V，当ui=-10V时，uo等于（）。

A:-6V B:6V C:-0.7V D:0.7V

如图7-16所示运算放大器电路中，已知ui1=1V，Ui2=2V，ui3=3V，ui4=4V，R1=R2=2kΩ，R3=R4=RF=1kΩ，求u0=（）。

A:0V B:5.5V C:-5.5V D:9V

电路如题2-26图所示，Ui1=2V，Ui2=1V。输出电压Uo=（）。

A:12V B:-12V C:-6V D:+6V