निम्नलिखित में से कौन सी अवधारणा सीमाओं को कठोर और स्थिर मानने के विचार को चुनौती देती है?

Given below are two statements, one labeled as Assertion (A) and the other as Reason (R): Assertion (A): The terrorist attacks of September 11, 2001 (9/11) fundamentally impacted international security and reshaped US foreign policy. Reason (R): Globalization and modern technology have empowered non-state actors to wage asymmetric warfare across borders. Choose the correct option:

In which of his works did Kenneth Waltz construct the 'Levels of Analysis' framework for international relations?