设计钢结构时，关于其安全等级的确定，正确的说法是(    )。
   Ⅰ．一般工业与民用建筑钢结构的安全等级可取一级
   Ⅱ．一般工业与民用建筑钢结构的安全等级可取二级
   Ⅲ．一般工业与民用建筑钢结构的安全等级可取三级
   Ⅳ．特殊建筑钢结构的安全等级可根据具体情况另行确定
   A．Ⅰ、Ⅳ    B．Ⅱ、Ⅳ    C．Ⅲ、Ⅳ    D．Ⅳ

根据以下资料，回答下列各题。The earliest immigrants to North America found Indians already living there．The Indians numbered about 500,000 at that time．Their society was a primitive society, but they lived peacefully and welcomed the white strangers to the land．However, these early immigrants from Europe didnt want to share the land with the natives．They killed off many of the Indians, seized their land or pushed them off to lands farther away．Today the Indians, not more than half a million, live in poverty and misery on the land on which they were once masters．The earliest immigrants were the Spanish, who settled in the southern part of what is now the US．The next large group were the English, after the English came the French, Dutch, Irish, Germans, and other nationality groups, mostly European．Another early group to arrive were the Negroes．But they were brought in as slaves from Africa．They didnt win freedom till generations later．Who were the earliest people living in North America?A.The Spanish．B.The English．C.The Negroes．D.The Indians． 点击查看答案

Modem的传输速率与上网速度密切相关，使用56K的Modem，其传输数据的速率______。 A．至少为14.4K B．至少为33.6K C．至少为56K D．不确定

A.至少为14.4K
B.至少为33.6K

C.至少为56K

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