请问大家几道语法题

3gh4rdUID: 203725

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

DajUID: 18915

1  allergy to milk
example : be allergic to milk
suggestion : get a grammer book ba

2 donot know how to  explain  , but obviously D is very bad
suggestion , read more , get the feeling

3 sorry , hard for me