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. | 
