This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Passage: 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 feature enables an MCU to allow for multiple parties to be seen on screen at the same time?
Continuous Presence

Passage: Another civil war ensued after the death of Karim Khan in 1779, out of which Aqa Mohammad Khan emerged, founding the Qajar Dynasty in 1794. In 1795, following the disobedience of the Georgian subjects and their alliance with the Russians, the Qajars captured Tblisi by the Battle of Krtsanisi, and drove the Russians out of the entire Caucasus, reestablishing a short-lived Iranian suzerainty over the region. The Russo-Persian wars of 18041813 and 18261828 resulted in large irrevocable territorial losses for Iran in the Caucasus, comprising all of Transcaucasia and Dagestan, which made part of the very concept of Iran for centuries, and thus substantial gains for the neighboring Russian Empire. Question: Whose death in 1779 led to a civil war in Iran?
Karim Khan

Passage: To create green sparks, fireworks use barium salts, such as barium chlorate, barium nitrate crystals, or barium chloride, also used for green fireplace logs. Copper salts typically burn blue, but cupric chloride (also known as "campfire blue") can also produce green flames. Green pyrotechnic flares can use a mix ratio 75:25 of boron and potassium nitrate. Smoke can be turned green by a mixture: solvent yellow 33, solvent green 3, lactose, magnesium carbonate plus sodium carbonate added to potassium chlorate. Question: Which copper salt can produce green glames?
cupric chloride