Why the explosion occurred was______the laboratory attendants had been careless.

A . eliminating sparks and fire in the vicinity of cargo tanks B . removing all hydrocarbon gases from the cargo tanks C . blanketing cargo tanks with inert foam D . reducing the oxygen concentration below levels necessary for combustio

A . lighter than air B . heavier than air C . odorless D . nontoxic

A . (1) only B . (2) only C . both (1) and (2) D . neither (1) or (2)

A . in boiler drums B . in refrigerating plants C . in starting air pipes D . in air cooler

A、for B、on C、at D、about

A . immediately open all crankcase relief ports B . increase crankcase exhauster speed to draw cool air into the engine C . allow the engine to cool naturally D . increase crank case scavenge air to remove unburned gase

A . excessive purging before lighting off B . insufficient trail for ignition period C . a faulty transformer in the ignition circuit D . insufficient purging before lighting off

A . flammable vapor by volume in air B . oxygen present to support combustion C . the temperature of the flash point D . the lower limit of explosibility of the mixture

A . auto-ignition point B . flash point C . lower explosive limit (LEL) D . threshold limit value (TLV)

A .  The job priority is 1 and the resource consumer group CPU emphasis allocation is a low percentage. B .  The job affinity is to a service and one node in that service is unavailable. C .  The job affinity is to an instance and that instance is unavailable. D .  There is no service affinity. E .  None of the above.

A . There is an error in the router DRAM. B . Te IOS image is corrupt. C . The configuration register is set to 0x2142. D . The TFTP server that contains the router configuration file is unreachable. E . A boot system configuration command has placed the router into setup mode.

A . rich to burn B . lean to burn C . cool to burn D . dense to bur

A．the adoption of a policy of aggressive predator elimination. B．the increased number of National Parks. C．the deceasing number of visitors to National Parks. D．the heavy exploitation of endangered animals in the 20 century. 此题为多项选择题。

With the explosion of digital media in recent years, a growing number of students are spending their time in front of the small screen---whether it’s a Smartphone or tablet. In just two years, the number of US children using digital media has doubled to 72 percent, according to a survey by Common Sense Media. On average, students spend about two hours a day in front of the screen. Watching TV makes up half of this time. But gradually, the time children spend watching TV is decreasing, with more and more time being given to digital media. Some of the common things kids do with digital media are playing games, watching videos and sending messages to friends. The digital world can be used very effectively. In the survey, 74 percent of teachers said that digital media would improve students’ learning. As students can quickly get hold of information they need. However, without guidance from teachers or parents, digital media may have bad influence on students’ attention span and communication skills. So it’s always best to use your smartphone and tablet carefully. When using digital media, you need to find a balance. Just like study, too much can lead to information overload, and give you a headache. Also, make sure your smartphone or tablet doesn’t take priority over more important tasks. Give your eyes a rest, and remember: offline is just as fun as online. 1. Two years ago, the number of US children who use digital media made up _____.{A; B; C} A. 72% B. 36% C. 74% 2. Which is not TRUE according to the passage？{A; B; C} A. Using digital media is good for students’ learning. B. Using digital media can improve students’ communication skills. C. Students should use their digital media under adults’ guidance. 3. The underlined word “overload” in the last paragraph means _____ in Chinese.{A; B; C} A. 重叠 B. 夸大 C. 超负荷 4. The article mentions that kids usually use digital media to _____.{A; B; C} ①play games ②send message to friends ③watch videos ④shop online A. ①②③ B. ①②③④ C. ①③④ 5. Why is the time children spend watching TV decreasing？{A; B; C} A. Because they need a balance of study and entertainment. B. Because the TV shows aren’t interesting at all. C. Because they turn to spend more time on digital media.

A．Y B．N C．NG

A:正确; B:错误

A.quarreling becomes inevitable B.it is not longer a conflict between two individuals C.people begin to hate each other D.no solution is possible

A．Many scholars like to find an isolated place in a remote area so that they can concentrate on their researches. B．Planes can take scholars here and there. C．There are more people working in similar fields than before. D．There are more learning centres than before. 此题为多项选择题。

是 否

Although no one is certain why migration occurs, there are several theories. One theory is based upon the premise that prehistoric birds of the northen Hemisphere were forced south during the Ice Age, when glaciers covered large parts of Europe, Asia, and North America. As the glaciers melted, the birds came back to their homelands, spent the summer, and then went south again as the ice advanced in winter. In time, the migration became a habit, and now, although the glaciers have disappeared, the habit continues. Another theory proposes that the ancestral home of all modern birds was the tropics. When the region became overpopulated, many species were crowded north. During the summer, there was plenty of food, but during the winter, scarcity forced them to return to the tropics. A more recent theory, known as photoperiodism, suggests a relationship between increasing daylight and the stimulation of certain glands in the birds' bodies that may prepare them for migration. One scientist has been able to cause midwinter migrations by exposing birds to artificial periods of daylight. He has concluded that changes occur in the bodies of birds due to seasonal changes in the length of daylight. According to one theory, when the glaciers disappeared, birds ______. () A．stopped migrating B．continued migrating C．began migrating again D．migrated south and stay there