求教885-21-6，提问版的连接打不开。

5.     By the mid-seventeenth century, Amsterdam had built a new town hall so large that only St. Peter’s in Rome, the Escorial in Spain, and the Palazza Ducale in Venice could rival it for scale or magnificence.

(A) could rival it for

(B) were the rivals of it in their

(C) were its rival as to

(D) could be its rivals in their（A）

(E) were rivaling its

rival的用法是什么呀？

6.     The Audubon Society and other conservation groups, concerned over what they have perceived to be the serious threatening of the environment as posed by the policies of the government, are preparing for a major political effort.

(A) have perceived to be the serious threatening of the environment as

(B) perceived as the serious threat to the environment as

(C) perceive being the serious threat to the environment

(D) are perceiving as the serious threatening of the environment（E）

(E) perceive as the serious threat to the environment

concerned that perceive....是什么结构？perceive 为何用原型呀？

Here are some explanations from Webmaster about rival as a verb:

intransitive senses   : to act as a rival : COMPETE
transitive senses  
1 : to be in competition with
2 : to strive to equal or excel : EMULATE
3 : to possess qualities or aptitudes that approach or equal (those of another)

As per the 2nd question, the main structure of the sentence is sth like this: the groups, (concerned over <what they perceive as serious threats>), are preparing...  erceive as is in PRESENT form.

hope it helps...

可以将链接直接复制、粘贴到地址栏里。