A cheap printed sensor (传感器) could transmit wildfire warnings. Wildfires have recently destroyed the forests across the world, a

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问题     A cheap printed sensor (传感器) could transmit wildfire warnings. Wildfires have recently destroyed the forests across the world, and their gravity is increasing. Hoping to reduce harm, researchers led by Yapei Wang, a Chinese chemist of Renmin University, say they have developed an inexpensive sensor to detect (监测)  such fires earlier with less effort.
    Current detection methods rely heavily on human watchfulness, which can delay an effective response. Most wildfires are reported by the general public, and other alarms come from routine foot patrols and watchtower observers. Passing planes and satellites also occasionally spot something, but "the fire first appears on the ground, " Wang says. "When you see the fire from the sky, it is too late. "
    The team says its new sensor can be placed near tree trunks’ bases and send a wireless signal to a nearby receiver if there is a quick temperature increase. That heat also powers the sensor itself, without replacing batteries. The team printed the substances onto ordinary paper to create a sensor for just $0.40.
    But improving coordination among the different companies involved in firefighting is even more important to deal with, says Graham Kent, an earthquake expert at the University of Nevada, Reno, who was not part of the study. Kent is director of ALERT Wildfire, a network that uses cameras and crowd sourcing to watch for fires in California, Nevada and Oregon. "The whole way that you respond to a fire until it’s put out is like a ballet, " he says. "You’d have to choreograph (设计) it just so, with resources accurately used at the right time and place in the right order from detection to confirmation to assignment to extinguishment (熄灭). Fire detection is just step one. "
    Wang says his team’s next steps are to extend the device’s signal range beyond the current 100 meters, which can limit practical use, and to develop a protective shield (防护罩) for it. The transmitter’ s effectiveness,  he notes,  will also need to be examined in the field ahead.
Why is lightweight luggage important for the travelling businesswoman?

选项 A、It provides space for dirty clothes.
B、It is easy to move.
C、It can double as a briefcase.
D、It is usually big enough to carry all business documents.

答案B

解析 根据文章第三段第二句“This starts with lightweight luggage which you can easily manage even when fully packed.”可知,出差时携带轻便行李自然为的是搬运方便。因此选B。
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