What happened in Chernobyl, Ukraine, in 1986?

In 1986, a nuclear reactor at the Chernobyl power plant exploded during a safety test, releasing radioactive material. The accident caused 30 immediate deaths, making A, “The explosion of a nuclear reactor killed 30 people,” the best answer. The other choices describe different kinds of industrial or mining disasters, not the Chernobyl accident.

AI-written and checked against the verified answer.