原文：Seven countires signed a treaty binding each of them to perform specified actions on a certain fixed date, with the actions of each conditional on simultaneous action taken by the other countries. Each country was also to notify the six other countires when it had completed its action.

问题：The simultaneous-action provision of the treaty leaves open the possibility that ...

五个备选答案：


A.the compliance date was subject to postponement, according to the terms of the treaty.

B.one of the countries might not be required to make any changes or take any steps in order to comply with the treaty, whereas all the other countries are so required.

C.each country might have a well-founded excuse, based on the provision, for its own lack of compliance.

D.the treaty specified that the signal for one of the countries to initiate action was notification by the other countries that they had completed action.

E.there was ambiguity with respect to the date after which all actions contemplated in the treaty are to be complete.

CXD书里的答案是C，但是没有讲解。

哪位牛人能给解释一下啊，谢了先！