about space tasks and try simulated(模拟) flying to space with the crew from all over the world. The Aviation Challenge program gives trainees the chance to earn their Aviation badge. They learn the principles of flight and test their operating skills in the cockpit(驾驶舱) of a variety of flight simulators. Trainees also get a good start on their Wilderness Survival badge as they learn about water- and land-survival through designed tasks and their search and rescue of ＂downed＂ pilot.

　　With all the programs, teamwork is key as trainees learn the importance of leadership and being part of a bigger task.

　　All this fun is available for ages 9 to 18. Families can enjoy the experience together, too, with Family Camp programs for families with children as young as 7.

　　Stay an hour or stay a week - there is something here for everyone!

25. Why do people come to SAC?

　　A. To experience adventures. B. To look for jobs in aviation.

　　C. To get a degree in engineering. D. To learn more about medicine.

26. To earn a Space Exploration badge, a trainee needs to .

　　A. fly to space B. get an Aviation badge first

　　C. study the principles of flight D. build and fire model rockets

27. What is the most important for trainees?

　　A. Leadership. B. Team spirit. C. Task planning. D. Survival skills.

　　C

　　Plastic-Eating Worms

　　Humans produce more than 300 million tons of plastic every year. Almost half of that winds up in landfills(垃圾填埋场), and up to 12 million tons pollute the oceans. So far there is no effective way to get rid of it, but a new study suggests an answer may lie in the stomachs of some hungry worms.

　　Researchers in Spain and England recently found that the worms of the greater wax moth（大蜡螟幼虫） can break down polyethylene（聚乙烯）, which accounts for 40% of plastics. The team left 100 wax worms on a commercial polyethylene shopping bag for 12 hours, and the worms consumed and broke down about 92 milligrams, or almost 3% of it. To confirm that the worms' chewing alone was not responsible for the polyethylene breakdown, the researchers made some worms into paste(糊状物) and applied it to plastic films. 14 hours later the films had lost 13% of their mass - apparently broken down by enzymes (酶) from the worms' stomachs. Their findings were published in Current Biology in 2017.

　　Federica Bertocchini, co-author of the study, says the worms' ability to break down their everyday food - beeswax - also allows them to break down plastic. ＂Wax is a complex mixture, but the basic bond in polyethylene, the carbon-carbon bond, is there as well, ＂she explains, ＂The wax worm evolved a method or system to break this bond. ＂

Jennifer DeBruyn, a microbiologist at the University of Tennessee, who was not involved in the study, says it is not surprising that such worms can break down polyethylene. But compared with