The correct option is: "aboveground"
The Comprehensive Nuclear-Test-Ban Treaty is an international treaty, signed for the first time on September 10, 1996, which prohibits the conduct of nuclear tests in and by the signatory countries.
The treaty was opened for signature in New York on September 24, 1996, when it was signed by 71 states, including five of the eight with nuclear capacity. Currently, the CTBT has been signed by 178 countries out of a total of 195, and ratified by 144. On January 16, 2007 ratification of the treaty was completed by all European countries, with the ratification of Moldova.
