手术时无菌操作时，穿无菌手术衣后，手术者双手可交叉置于腋下。请判断是对是错?

Many parents try hard to protect their kids from TV and Internet advertising. But how can you protect a child form. a large fast-food ad painted on her school locker(小柜)? Or a toy ad on the side of his school bus? 点击查看答案

It can be hard to feel much sympathy for bats. Like snakes or spiders or sharks, there’s something quite alarming about bats, something that holds back empathy. Bats aren’t actually,“flying rodents(啮齿动物),” but you likely won’t see them on the next endangered species poster.But bats in the U.S. are in serious trouble, thanks largely to a catastrophic disease called white-nose syndrome (WNS), which has killed at least one million bats, mostly in the northeast, and death rates among some affected winter colonies can be as high as 70%. One species—the little brown bat or Myotis lucifugus—has declined so quickly that it is headed for extinction. And the disease keeps spreading, with wildlife experts helpless to stop it—after starting in upstate New York in 2006, the disease was just confirmed as far west as Ohio yesterday.You might say: so what? Other than people who study bats—would anyone miss them when they’re gone? As it turns out, all of us would—at least if you like food. A new article in Science shows that bats have an important role to play in agriculture—one worth at least $3.7 billion a year, if not far more. That’s how much the extinction of bats throughout North America could cost the region’s food system, according to an analysis by a group of researchers led by Justin Boyles of the University of Pretoria in South Africa. The logic is simple: bats eat bugs—tons and tons of bugs—and that includes crop and forests pests. (A single colony of 150 brown bats in Indianan has been estimated to eat nearly 1.3 million pest insects a year.) Remove the bats, and you remove one of nature’s most effective biological pesticides—which would have to be replaced by actual pesticides, at an economic and environmental expense.It’s not just WNS that is striking down bats. Wind turbines(涡轮机)are apparently killing migratory(迁徙的)bats as well—by 2020, an estimated 33,000 to 111,000 bats are predicted to be killed by turbines in the mid-Atlantic Highlands alone. The authors in the Science paper worry that as wind power develop fast in the U.S., more bats will end up killed by the blades. But WNS seems like the more immediate threat. But it’s still a mystery how WNS spread, and how to stop it—those the U.S. Fish and Wildlife Service, among other government agencies, is on the case. We may not like bats—but we definitely need them.43. What is the author’s opinion about bats? 点击查看答案