Pakistan conducted nuclear tests in:

Pakistan conducted its first series of nuclear weapons tests, codenamed Chagai-I, on May 28, 1998. This event was a significant development in the country's defense capabilities and regional geopolitics.

• 1998 (option B) is the correct year when Pakistan officially became a nuclear power, responding to similar tests conducted by India earlier that month.
• Options A (1996), C (1999), and D (1995) are incorrect. While there was ongoing research and development, the actual tests that confirmed Pakistan's nuclear status occurred specifically in 1998.

These tests marked a critical juncture in the history of nuclear proliferation and South Asian security.