以下三题分别是新东方语法讲义中的180、186、187，希望哪位帮我看一下，谢谢。
1. Researchers have questioned the use of costly and experimental diagnostic tests to identify food allergies, such as milk, that supposedly disrupt normal behavior.
A. to identify food allergies, such as
C. to identify food allergies, such as to
该题真确答案选C，但这里为什么要加个to呢？

2. According to the Better Business Bureau,if you fail to advertise the highest price in a range of prices for a service or product as prominently as that of the lowest, it violates the New York Consumer Protection.
C. failure to advertise the highest price in a range of prices for a service or product as prominently as the lowest
D. faliure to advertise as prominently the highest price in a range of prices for a service or product as the lowest
该题正确答案选C，可我就不知道C和D有什么区别呢。

3. In this most recent approach , the comet Crommelin passed the Earth at about the same distance and in about the same position, some 25 degrees above the horizon, that the Halley's comet will pass the next time it appears.
D. as will Halley's comet
E. as Halley's comet will do
正确答案是D， 请问E错在哪里呢

以下三题分别是新东方语法讲义中的180、186、187，希望哪位帮我看一下，谢谢。
1. Researchers have questioned the use of costly and experimental diagnostic tests to identify food allergies, such as milk, that supposedly disrupt normal behavior.
A. to identify food allergies, such as
C. to identify food allergies, such as to
该题真确答案选C，但这里为什么要加个to呢？

因为是ＡＬＬＥＲＧＹ　ＴＯ　表示对什么过敏．不加ＴＯ　就是在说ＡＬＬＥＲＹ　是牛奶～！讲不通～！

2. According to the Better Business Bureau,if you fail to advertise the highest price in a range of prices for a service or product as prominently as that of the lowest, it violates the New York Consumer Protection.
C. failure to advertise the highest price in a range of prices for a service or product as prominently as the lowest
D. faliure to advertise as prominently the highest price in a range of prices for a service or product as the lowest
该题正确答案选C，可我就不知道C和D有什么区别呢。

Ｄ是ＨＩＧＨＥＳＴ　ＰＲＩＣＥ　和ＬＯＷＥＳＴ　ＰＲＩＣＥ　比较．Ｃ是两件事情的比较｀！而且省略了很多，补全是～advertise the highest price in a range of prices for a service or product as prominently as advertise　the lowest price in a range of prices for a service or product as

3. In this most recent approach , the comet Crommelin passed the Earth at about the same distance and in about the same position, some 25 degrees above the horizon, that the Halley's comet will pass the next time it appears.
D. as will Halley's comet
E. as Halley's comet will do
正确答案是D， 请问E错在哪里呢

象这样的省略一般省到助动词这里就是ＷＩＬＬ．