International Organizations

To determine which country is not a member of the "Quadrilateral Security Dialogue" (QUAD), we examine each of the given options. The QUAD is an informal strategic forum comprising four countries: the United States, Japan, India, and Australia. These countries collaborate on security and defense, primarily in the Indo-Pacific region.

1. Japan: Member of the QUAD.
2. India: Member of the QUAD.
3. Australia: Member of the QUAD.
4. China: Not a member of the QUAD. It is often considered a rival or competitor to the countries in the QUAD, which aim to counterbalance China's influence in the Indo-Pacific.

Therefore, the country that is not a member of the QUAD is China.