题目内容
在不考虑噪声的条件下，光纤能达到的极限数据率是(1)；光纤上信号在传输过程中有能量损失，工程上在无中继条件下信号在光纤上能传输的最远距离大约是(2)千米。
(1)
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设计一个网络时，分配给其中一台主机的IP地址为192.55.12.120，子网掩码为 255.255.255.240。则该主机的主机号是(1)；可以直接接收该主机广播信息的地址范围是(2)。
(1)
网络管理功能使用ASN.1表示原始数据，整数49使用ASN.1表示的结果是(1)； SNMP协议的GetBulkRequest一次从设备上读取的数据是(2)。
(1)
【H12】
Charter Schools
American public education has changed in recent years. One change is that increasing numbers of American parents and teachers are starting independent public schools called charter schools.
In 1991, there were【H1】charter schools in the United States. Today, more than 2,300 charter schools【H2】in 34 states ar/d the District of Columbia, 2,575,000 students【H3】these schools. The students are from 5 years【H4】age through 18 or older.
A charter school is created by groups of parents, teachers and community members. It is similar【H5】some ways to a traditional public school. It receives tax money to operate just as【H6】public schools do. The amount it receives depends【H7】the number of students. The charter school must prove【H8】local or state governments that its students are learning. These governments provide the school【H9】the agreement, or charter that permits it to operate.
Unlike a traditional public school,【H10】, the charte'r school does not have to obey most laws governing public schools. Local, state or federal governments cannot tell it what to teach.
Each school can choose its own goals and decide the ways it wants to【H11】those goals. Class sizes usually are smaller than in many traditional public schools. Many students and parents say teachers in charter schools can be more creative.
However, state education agencies, local education-governing committees and unions often
【H12】charter schools. They say these schools may receive money badly needed by traditional public schools. Experts say some charter schools are doing well while others are struggling.
Congress provided 200 million dollars for establishing charter schools in the 2002 federal budget.
【H13】often the schools say they tack enough money for their programs. Many also lack needed space.
【H14】, many of the 36 charter schools in the District of Columbia hold classes in crowded buildings. These schools have almost 11, 000 students. District officials say they have provided 14 former school buildings【H15】charter education. Yet, charter-school supporters say officials should try harder to find more space.
【H1】
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