请教这几道语法题,希望能给予回复,谢谢!感谢上次给我解答语法题的朋友,谢谢!

1. In (its)(A) pure state aluminum is a weak metal, but (when)(B) combined with elements such as copper or magnesium, it (is formed)(C) alloys of great (strength)(D).

答案：C

2.In geometry, an ellipse may defined as the locus of all points,( )distances from two fixed point is constant.

A. which as the sum of B. of the sum which

C. the sum of whose D. whose sum that the

答案：C

3.An image on a national flog can symbolize political ideal that ( )express.

A.take many words to otherwise would

B.would take to many otherwise words

C.many words to take would otherwise

D. would otherwise take many words to

答案：D

4.(Native)(A) to South America (and cultivated)(B) there for thousands of years, the peanut (is said)(C) to (have introduced)(D) to North America by early explorers.

答案：D

5.Lowell, Massachusetts, known as the “Spindle City” (since)(A) 1822 (when)(B) its first textile mills were built, (attracted)(C) world wide attention (as textile)(D) center.

答案：D

两个填空题正确选项的意思：

2、C. whose指代points 主语是the sum 系表is constant.

（在椭圆中）所有两点之间距离的总和不变。

3、D. that指代political idea 在从句中作express的宾语，谓语would take 不定式to express表被动。等于(that )to be expressed.

如果不用An image on a national flog，需要用很多文字来表达（相同的）political idea 。

意思是说，图象通过象征手法表达本来需要大量文字才能表达清楚的政治观点。