以下的句子中，每句都有一个错误，请把这个错误改过来。

　　1.A major step in the development of algebra was the evolution of an accurate understand of negative quantities.

　　2. If television had been invented a thousand years ago, will nations be significantly more homogeneous than they are now?

　　3. To the citizens of the United States, the bald eagle, America's national bird, symbolize strength and freedom.

　　4. authenticity stained glass is colored while the glass is in a liquid state.

　　5. On most scales, zero marks the starting point or the neutralize position.

　　6. Traditionally, ethnographers and linguists have paid little attention to cultural interpretations given to silence, or to the types of social contexts in which tends to occur.

　　7. The research of Percy Julian has contributed to the creation of drugs that are in widespread use over victims of arthritis.

　　8. The Appalachian Trail, extending approximately 2020 miles from Maine to Georgia, is the longer continuous marked footpath in the world.

　　9. When rainbows appear, they are always in the part of the sky opposite directly the Sun.

　　10. Benjamin Franklin drew a political cartoon that is credited raising 10000 volunteers for the American Revolutionary War.

　　11. Luminescence refers to the emission of light by means another than heat.

　　12. Since 1971 the regional corporations set up in Alaska by Congress managing everything from fishing to banking.

　　1、understand-->understanding.词性混用：形容词必须修饰名词；of前面也必须是名词。of后面：通用的，大家一看就明白的不用加冠词或定冠词。

　　2、will-->would,be-->have been(也可不改)。句子结构：IF引导的虚拟结构。虚拟语气只对它的主句起作用。所以"than they are now"没有错。

　　3、symbolize-->symbolizes抽象名词如果不特指，不需加任何冠词和定冠词。strenghth and freedom是抽象名词。

　　4、Authenticity-->authentically修饰stained

　　5、neutralize-->neutralizing属词性误用

　　6、which tend to-->which it tend to属缺指代词的错误注意given to silence前省略了which are:which are/is的引导词和伴随的系动词可随时省略，越省略越正确。(名词+过去分词/现在分词修饰名词做定语时，常常是定语从句的省略)如果which前加了介词，后面的句子必须有主语。

　　7、over-->by/on属介词误用

　　8、longer-->longest continous marked path=continous and marked path

　　9、opposite directly-->directly opposite介词词组不能分开；如果有副词修饰介词词组，一定要把副词放到介词词组的后面。

　　10、is credited raising--is credited with raising属固定搭配与词组的使用is没错，但也可用was，动作人可以是现在或将来的人。

　　11、another-->other

　　by means other than靠除了…的方法

　　by means of靠…方法

　　means的四个词组：by means of other than

　　by means of

　　by all means一定

　　by no means绝不

　　12、set up-->were set up名词+ing可指一个行业：fishing渔业banking银行业