Input: Read this: Simultaneous videoconferencing among three or more remote points is possible by means of a Multipoint Control Unit (MCU). This is a bridge that interconnects calls from several sources (in a similar way to the audio conference call). All parties call the MCU, or the MCU can also call the parties which are going to participate, in sequence. There are MCU bridges for IP and ISDN-based videoconferencing. There are MCUs which are pure software, and others which are a combination of hardware and software. An MCU is characterised according to the number of simultaneous calls it can handle, its ability to conduct transposing of data rates and protocols, and features such as Continuous Presence, in which multiple parties can be seen on-screen at once. MCUs can be stand-alone hardware devices, or they can be embedded into dedicated videoconferencing units.
Question: What is one type of simultaneous call that acts as a bridge?

Output: unanswerable


Input: Read this: In 1975, the band left for a world tour with each member in Zandra Rhodes-created costumes and accompanied with banks of lights and effects. They toured the US as headliners, and played in Canada for the first time. In September, after an acromonious split with Trident, the band negotiated themselves out of their Trident Studios contract and searched for new management. One of the options they considered was an offer from Led Zeppelin's manager, Peter Grant. Grant wanted them to sign with Led Zeppelin's own production company, Swan Song Records. The band found the contract unacceptable and instead contacted Elton John's manager, John Reid, who accepted the position.
Question: Who created the costumes for Queen's 1975 tour?

Output: Zandra Rhodes


Input: Read this: The indigenous peoples of the Americas are the descendants of the pre-Columbian inhabitants of the Americas. Pueblos indígenas (indigenous peoples) is a common term in Spanish-speaking countries. Aborigen (aboriginal/native) is used in Argentina, whereas "Amerindian" is used in Quebec, The Guianas, and the English-speaking Caribbean. Indigenous peoples are commonly known in Canada as Aboriginal peoples, which include First Nations, Inuit, and Métis peoples. Indigenous peoples of the United States are commonly known as Native Americans or American Indians, and Alaska Natives.
Question: How are the indigenous people most commonly referred to by citizens of the U.S.?

Output: Native Americans


Input: Read this: Destructive testing attempts to cause the software or a sub-system to fail. It verifies that the software functions properly even when it receives invalid or unexpected inputs, thereby establishing the robustness of input validation and error-management routines.[citation needed] Software fault injection, in the form of fuzzing, is an example of failure testing. Various commercial non-functional testing tools are linked from the software fault injection page; there are also numerous open-source and free software tools available that perform destructive testing.
Question: There are very few open-source and free tools that do what?

Output:
unanswerable