请问为什么选A不选C呢

问题如下：

QuestionIn the context of trading blocs, a common market would likely encompass characteristics of a:

选项：

A.customs union.

B.monetary union.

C.economic union.

解释：

1. Correct, as a common market represents a more advanced integration stage that integrates all the elements of a customs union and further facilitates the unrestricted flow of resources among member countries.
2. Incorrect, since a common market includes the features of a customs union coupled with the unobstructed flow of resources. When an economic union adopts a shared currency, it transforms into a monetary union.
3. Incorrect, given that a common market merges the elements of a customs union with the free mobility of resources. The alignment of economic strategies and the establishment of joint economic institutions are hallmarks of an economic union. This implies that an economic union demands an even more comprehensive integration, assimilating all the features of a common market while also necessitating the presence of shared economic institutions and synchronized economic strategies among member states.

A正确，因为共同市场代表了一个更高级的一体化阶段，它整合了关税同盟的所有要素，并进一步促进了资源在成员国之间的不受限制的流动。
B不正确，因为共同市场包括关税同盟的特征，加上资源畅通无阻的流动。当一个经济联盟采用共同货币时，它就转变为一个货币联盟。
C不正确，因为共同市场将关税同盟的要素与资源的自由流动结合在一起。经济战略的协调和共同经济机构的建立是经济联盟的标志。这意味着一个经济联盟需要更全面的一体化，吸收共同市场的所有特征，同时也需要成员国之间存在共享的经济制度和同步的经济战略。