Help me to crack several question

ca3ltoys

Help me crack and explain the following question from the princeton review-Verbal workout for the Gmat

1.  A growing number of urban school districts have embraced the practice of “social promotion.” Whereby a student is automatically promoted to the next highest grade regardless of whether he or she has passed or failed English class. This policy is flawed, because the only criterion that a student must fulfill in order to advance is to pass a state-wide standardized test.

The answer to which of the following questions would be most useful in evaluating the validity of “social promotion”?

(A)    Do students have to option of taking a standardized test in a language other than English?
(B)    What is the rate of graduation from schools at which “social promotion” is commonly practiced?
(C)    How rigorous are the questions on these standardized tests that pertain to English skills?
(D)    How prevalent is “social promotion” among school districts in more suburban areas?
(E)    If a student fails a standardized test, is he or she given the chance to take it again before having to be kept back?


the answer is C, I wondered why B is wrong?

2. Country L used to import wheat from Country S because Country S’s price per bale was the cheapest available. When Country S raised its price by 25 percent, however, Country L decided to transfer its business to Country D, which now boasted the best deal available.

Which of the following, if true, would be best supported by the assertions above?
(A)    the cost to harvest a bale of wheat in Country S increased by 25 percent
(B)    If Country S were to lower its price below Country D’s price, then Country L would resume its import relationship with Country S
(C)    If Country L could somehow reduce the cost of producing domestic wheat by 25 percent, it wouldn’t need to rely on any wheat imports
(D)    Country S and Country D do not import or export any wheat from each other.
(E)    If  Country D were to increase its price per bale of wheat by 25 percent, then a bale of wheat from Country S would once again be less expensive

the answer is E, I wondered why answer B is wrong??

3. Last month, the Hungarian embassy had to be emptied because of a perceived threat of a bomb in the building. Therefore, anyone who targets the Nigerian embassy next door will create similar chaos.

Which of the following, if true, would most weaken the conclusion above?

The answer is : In response to the trouble at the Hungarian embassy, each of the other embassies on the block tightened security by doubling the number of watchmen who patrol the border of the property.

help me explain it.

marshial

1.B 无关选项
2.成本原则，E正确
3、削弱的合情合理。

ca3ltoys

It's too vague to understand, please explain for me in detail.