决定锚段长度的主要因素是什么？

阅读理解。

根据短文内容。判断下列句子的正误。正确的用“T”错误的用“F”。(每小题1分。共5分)

     Most people in America speak only one language: English. They do not learn to speak a second language.

High schools teach languages. But why?

     First, most Americans never travel to other countries. America is a very large country. Americans can

travel a long distance and not leave the United States. Why don't Americans speak other languages? They do

not need to learn a second language.

     Second, one of the countries next to America is Canada. Most people in Canada speak English. Some

Americans live near Canada. They travel there often. But they do not have to learn a new language.

     Third, many people in other parts of the world speak English. If Americans travel to other countries, they

can speak English there, too.

     Some Americans think that it is a mistake to speak only English. They believe it is very important to learn a

second language. Maybe someday other Americans will agree. Then more people will speak a second language

in America.

( )1. Most Americans never learn to speak a second language.

( )2. Many Americans like traveling to other countries except Canada.

( )3. In other parts of the world many people speak English.

( )4. Some Americans think it is a mistake to travel to other countries.

( )5. Many Americans find it difficult for them to learn a second language.

电子政务系统规划具有的特点和要求有（）。

A、综合性

B、系统性

C、变革性

D、可持续性

E、创新性

.—Were you able to borrow Helen’s camera?

—No,she said ______lend it to anyone.

A．she’ll rather not

B．she wouldn’t rather

C．she’d rather not

D．she doesn’t rather

下图是由Emil Zmaczynski设计的金字塔式元素周期表的一部分，图上标有第ⅥA族和几种元素的位置。请同答

下列问题

(1)请在上图中将铁元素所在族的位置全部涂黑。

(2)自从周期表诞生以来，关于氧元素在周期表中的位置，一直存在纷争，有人主张把它放在第ⅦA族，理由是：氢的最外层电子“饱和缺一”。请写出NaH的电子式__________。

(3)b元素的氢化物与其最高价氧化物的水化物可生成一种盐，土壤中施用该盐做化肥时，其阴离子在水田中的利用率低，说明土壤胶体粒子带____（“正”或“负”）电荷。

(4)下列叙述正确的是____。

A. h的最高价氧化物对应的水化物是一种强碱

B. 硒化氢的稳定性强于f的氢化物的稳定性

C. c的氢化物的水溶液是强酸

D. 原子半径：h>e>a

E. 相同条件下，d与f形成的化合物水溶液的pH大于d与g形成的化合物水溶液的pH，说明相同浓度氰化物水溶液的酸性f弱于g

(5)d的某化合物呈淡黄色，可与氯化亚铁溶液反应生成红褐色沉淀和能使带火星的木条复燃的气体，若沉淀和气体的物质的量之比为2:1，反应的离子方程式为____________________。

能够进行增、减磁操作的装置有（）。

A.励磁调节器就地按钮、远方DCS、同期装置、保护装置

B.励磁调节器就地按钮、远方DCS、同期装置

C.励磁调节器就地按钮、远方DCS、保护装置