灭火原理主要是化学中断法的灭火剂是:A、二氧化碳 B、1211 C、泡沫 D、沙土

以下哪项不符合早孕的诊断

A．停经

B．早孕反应

C．尿频

D．妊娠试验阳性

E．自觉胎动

America’s population hit the 300 million mark yesterday—at 7:46 a.m. Eastern time, according to Census Bureau estimates. Nobody knows exactly who became America’s 300 millionth citizen.
But demographers are summing up the milestone as a turning point that signals several trends to watch as the US—in contrast with Europe and Japan—deals with a steadily growing population.
Politically and demographically, experts say, the shifts will begin to have an impact on regions of the country not yet used to the new diversity provided by the influx of Hispanics and Asians, which has already transformed California, Arizona, Texas, Florida, and New York.
In coming years, Midwesterners, those in the Great Plains, rural areas, and small towns everywhere will begin to deal with the challenges of new ethnic and racial residents, says William Frey, a population expert at the Brookings Institution in Washington. And the country as a whole will begin to be more dominated by a young/old divide than the current liberal/conservative model that dominates political discourse.
"This means we are going to transform the current, red/blue political dichotomy to one where the nation is separated by age ... young vs. old," says Mr. Frey. "The issues of younger generations dealing with children and opportunities for minorities will clash with those of the aging baby boomers whose voters are concerned with issues of aging and Social Security and Medicare," he adds. "Both parties will have to adjust to this new dichotomy. "
The new milestone hasn’t generated much hoopla. That’s in sharp contrast to 1967, when President Johnson hailed the 200 millionth American, and Life magazine dispatched a cadre of photographers to find a baby born at the exact moment. One reason is that population growth has become controversial, especially in an election year when immigration is a hot-button issue and politicians are wary.
Commerce Secretary Carlos Gutierrez says the Bush administration is not playing down the milestone, though he had no plans for Tuesday. "I would hate to think that we are going to be low-key about this," he says, since growth helps the economy.
While it’s hard to prove that population growth spurs economic growth, the two often go hand in hand, according to experts quoted in the Monitor’s recently published series: "US population. 300 million." For example, a nation with a rising population can support its retirees far more easily than one with a declining population. That’s an advantage for the US, which is virtually the only developed nation expected to grow this century. But population growth has less rosy implications, the Monitor series points out. Some experts worry that the land can’t sustain the extra 100 million people expected by 2043. Another challenge is sprawl, the dominant model of development, which gobbles up forest and prairie.

Why does the Monitor say that "population growth has less rosy implications" (para. 8)

蔗糖（旋光度为＋66.5°）水解生成等摩尔的D-葡萄糖（旋光度为＋52.5°）和D-果糖（旋光度为－92°）的混合物。

（a）提出一方便的方法，以确定由小肠壁提取的转化酶水解蔗糖的速率。

（b）为什么由蔗糖水解形成的等摩尔D-葡萄糖和D-果糖的混合液在食品工业上被称之转化糖？

（c）转化酶（即蔗糖酶）作用于蔗糖溶液至混合液的旋光度变为0时，多少蔗糖被水解？

1945年9月，中国第四集团军司令王耀武命令，将总司令部迁往长沙，第四集团军是由哪一个军组建的呢？

影响加工精度的主要因素有哪些？