Input: Read this: Depleted uranium is also used as a shielding material in some containers used to store and transport radioactive materials. While the metal itself is radioactive, its high density makes it more effective than lead in halting radiation from strong sources such as radium. Other uses of depleted uranium include counterweights for aircraft control surfaces, as ballast for missile re-entry vehicles and as a shielding material. Due to its high density, this material is found in inertial guidance systems and in gyroscopic compasses. Depleted uranium is preferred over similarly dense metals due to its ability to be easily machined and cast as well as its relatively low cost. The main risk of exposure to depleted uranium is chemical poisoning by uranium oxide rather than radioactivity (uranium being only a weak alpha emitter).
Question: How is depleted uranium used in missile re-entry vehicles?

Output: ballast


Input: Read this: Following the end of the Cold War, the threat of direct conventional military confrontation with other states has been replaced by terrorism. Sir Richard Dannatt predicted British forces to be involved in combating "predatory non-state actors" for the foreseeable future, in what he called an "era of persistent conflict". He told the Chatham House think tank that the fight against al-Qaeda and other militant Islamist groups was "probably the fight of our generation".
Question: Who was involved with terrorism in the Cold War?

Output: unanswerable


Input: Read this: In the far north, there is a division between Berber-descendent Tuareg nomad populations and the darker-skinned Bella or Tamasheq people, due the historical spread of slavery in the region. An estimated 800,000 people in Mali are descended from slaves. Slavery in Mali has persisted for centuries. The Arabic population kept slaves well into the 20th century, until slavery was suppressed by French authorities around the mid-20th century. There still persist certain hereditary servitude relationships, and according to some estimates, even today approximately 200,000 Malians are still enslaved.
Question: What region of the country is historical slavery well known?

Output: far north


Input: Read this: On 1 July 1967, BBC Two became the first television channel in Europe to broadcast regularly in colour, using the West German PAL system that is still in use today although being gradually superseded by digital systems. (BBC One and ITV began 625-line colour broadcasts simultaneously on 15 November 1969). Unlike other terrestrial channels, BBC Two does not have soap opera or standard news programming, but a range of programmes intended to be eclectic and diverse (although if a programme has high audience ratings it is often eventually repositioned to BBC One). The different remit of BBC2 allowed its first controller, Sir David Attenborough to commission the first heavyweight documentaries and documentary series such as Civilisation, The Ascent of Man and Horizon.
Question: What did BBC One and ITV begin on 15 November 1967?

Output:
unanswerable