题型:阅读理解 题类:常考题 难易度:普通
Mosquitoes have an extraordinary ability to find humans far away and fly straight to their skin. Mosquitoes can do more than cause an itchy (发痒的)wound. Some mosquitoes spread several serious diseases, including Dengue, yellow fever and malaria.
Over one million people worldwide die from these diseases each year. New research now shows how mosquitoes choose who to bite.
Mosquitoes need blood to survive. They are attracted to human skin and breath. They smell the carbon dioxide gas, which all mammals breathe out. This gas is the main way for mosquitoes to know that a warm-blooded creature is nearby.
But mosquitoes also use their eyes and sense of touch. Michael Dickinson is a professor at the California Institute of Technology. His research shows how these small insects, with even smaller brains, use three senses to find a blood meal.
Michael Dickinson's team used plumes—a material that rises into the air of carbon dioxide gas into a wind tunnel (隧道). They then used cameras to record the mosquitoes. The insects followed the plume.
Then, the scientists placed dark objects on the lighter colored floor and walls of the tunnel. Mr. Dickinson said, at first, the mosquitoes showed no interest in the objects at all. “What was quite surprising is that the mosquitoes fly back and forth for hours. These are hungry females and they completely ignore the objects on the floor and wall of the tunnel. But the moment they get a hit of CO₂, they change their behavior quite obviously and now would become attracted to these little visual blobs (斑点).”
This suggested to the researchers that a mosquito's sense of smell is more important in the search for food. Once mosquitoes catch a smell of a human or animal, they also follow visual signals.
In order to help customers find what they want quickly, it's important to keep the thousands of titles in the Main Street Movies store organized properly. This section of the Employee Handbook will tell you how to organize videos.
Each Main street Movies store has three main sections:
1). New Releases Wall.
2). Film library.
3). Video Games.
New Releases Wall. Almost 70 percent of movie rentals are new releases, and that is the first place where most customers go when they enter the store. The center section of shelves on this wall holds Hottest Hits. When new titles come into the store, place them on this wall in alphabetical order. The shelves beside Hottest Hits are called Recent Releases. The New Releases Wall, including the Hottest Hits and Recent Releases shelves, holds about 350 titles.
Film Library. The thousands of titles in the Film Library are organized into categories. The films within each category are displayed alphabetically. Here are the categories and their two-letter computer codes:
AC | Action | DR | Drama | HO | Horror |
CH | Children | FA | Family | MU | Music |
CO | Comedy | FL | Foreign Language | SC | SCIENCE Fiction |
Foreign Language titles include films that were originally made in a foreign language and films with foreign language subtitles. A sticker on the back of each box tells which type of film it is.
Video Game. All the video games in Main street Movies are arranged in alphabetical order. Although video games represent only a small percentage of our inventory(库存), they are stolen more often than any other type of goods in our store. Therefore, video games are never displayed on the shelves. Shelves in the Video Game section hold cardboard with pictures and information about each game. When a customer wants to rent a particular game, you then find the game from the locked case behind the counter.
试题篮