聚合物的化学反应

以下几种游戏中，属于有规则游戏的有（ ）

A．结构游戏

B．智力游戏

C．体育游戏

D．表演游戏

E．音乐游戏

利用干细胞移植可以治疗白血病。治疗中需要进行全身放化疗、输入异体造血干细胞，并进行抗排异处理。下列有关说法不正确的是[ ]

A．移植异体干细胞可以避免自体干细胞中癌细胞的污染

B．对患者进行放化疗处理能够消灭癌细胞

C．输入的造血干细胞具有分化成各种血细胞的能力

D．治愈后患者体内的白细胞不会发生衰老和凋亡

关于家蚕发育过程，正确的是

A．卵→幼虫→蛹→成虫

B．卵→蛹→幼虫→成虫

C．若虫→卵→成虫

D．卵→若虫一成虫

下列图中表示SDH分插复用器的是（）。

A.A 

B.B 

C.C 

D.D 

On the first Earth Day, the U.S. was a poisoned nation. Dense air pollution blanketed cities like Los Angeles, where smog alerts were a fact of life. Dangerous pesticides like DDT were still in use, and water pollution was rampant—symbolized by raging fires on Cleveland’s Cuyahoga River. But the green movement that was energized by Earth Day— and the landmark federal actions that followed it—changed much of that. Today air pollution is down significantly in most urban areas, the water is cleaner, and even the Cuyahoga is home to fish again.

But if the land is healing, Americans may be sickening. Since World War Ⅱ, production of industrial chemicals has risen rapidly, and the U.S. generates or imports some 19 billion kg of them per day. These aren’t the sorts of chemicals that come to mind when we picture pollution—huge plants spilling contaminated wastewater into rivers. Rather, they’re the molecules that make good on the old "better living through chemistry" promise, appearing in items like unbreakable baby bottles and big-screen TVs. Those chemicals have a, habit of finding their way out of everyday products and into the environment—and ultimately into living organisms. A recent biomonitoring survey found traces of 212 environmental chemicals in Americans—including toxic metals, pesticides, etc. "It’s not the environment that’s contaminated so much," says the director of the Cincinnati Children’s Environmental Health Center. "It’s us."

As scientists get better at detecting the chemicals in our bodies, they’re discovering that even tiny quantities of toxins can have a potentially serious impact on our health—and our children’s future. Chemicals like bisphenol A (BPA) and phthalates—key ingredients in modern plastics—may disrupt the delicate endocrine system. A host of modern ills that have been rising unchecked for a generation—obesity, diabetes, attention-deficit disorder —could have chemical connections. "We don’t give environmental exposure the attention it deserves," says Dr. Philip Landrigan. "But there’s an emerging understanding that kids are uniquely susceptible to environmental hazards."

Washington has been slow to arrive at that conclusion. The Toxic Substances Control Act (TSCA), the 34-year-old vehicle for federal chemical regulation, has generally been a failure. The burden of proving chemicals dangerous falls almost entirely on the government. And the Environmental Protection Agency (EPA) has been able to issue restrictions on only a handful of chemicals and has lacked the power to ban even some dangerous cancer-causing substances.

But change is coming. The Obama Administration is taking a closer look at chemicals. More important, Congress may finally be ready to act. "We can’t permit this assault on our children’s health—and our own health—to continue," says Senator Frank Lautenberg.

According to Senator Frank Lautenberg, （）

A. actions should be taken to protect children from the environmental chemicals

B. more people begin to realize children’s susceptibility to environmental hazards

C. we should give more attention to environmental exposure

D. it’s more important and urgent to protect children’s health