OG13, 103题C选项？

julie0808

103. For a trade embargo against a particular country to succeed, a high degree of both international accord and ability to prevent goods from entering or leaving that country must be sustained. A total blockade of Patria’s ports is necessary to an embargo, but such an action would be likely to cause international discord over the embargo.

The claims above, if true, most strongly support which of the following conclusions?c

(A) The balance of opinion is likely to favor Patria in the event of a blockade.

(B) As long as international opinion is unanimously against Patria, a trade embargo is likely to succeed.

(C) A naval blockade of Patria’s ports would ensure that no goods enter or leave Patria.

(D) Any trade embargo against Patria would be likely to fail at some time.

(E) For a blockade of Patria’s ports to be successful, international opinion must be unanimous.

请各位NN 来帮帮忙， D选项我理解了。可是C 说得怎么看都并没有错啊。 原文说满足禁运的两个条件：1.国际协作 2.阻止商品的进入和出去
C选项说C港口的禁运会确保商品不能进出。  P的禁运也是对一个国家禁运的一种方式，所以C选项在这里我理解为是原文的改写。
OG上也说这个选项是simply defines the purpose of a blockade; 既然是simply define，说明和原文没有出入，即可以从原文得到。 那么为什么不能选C呢？

对逻辑题的出题思路真的有点不明白啊，请教各位NN，这种MUST BE TRUE题， 一般应该从什么角度去找答案呢？