Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: North Korea may already have 20 nuclear warheads - double as many as previously thought, Chinese nuclear experts have warned. The pariah state may also have the capability to produce enough weapons-grade uranium to double its arsenal by next year, The Wall Street Journal has reported. Chinese estimates of Pyongyang's nuclear production, relayed to US nuclear specialists, exceed most previous US forecasts of between 10 to 16 bombs, said the report, which cited people briefed on the matter. Scroll down for video A North Korean vehicle carrying a missile passes by during a mass military parade in Pyongyang's Kim Il Sung Square. The pariah state may have as many as 20 nuclear warheads, it has now been suggestedPariah state may have 20 warheads not 10 as previous US forecasts heldStockpile of weapons could grow to 50 or even 100 within next five yearsUS military believes secretive country has ability to miniaturise warhead and mount it on ballistic missile, though there have been no such tests yet 
 Question:_ has conducted three nuclear detonations, the most recent in February 2013.

North Korea