TASK DEFINITION: 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.
PROBLEM: 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?

SOLUTION: Continuous Presence

PROBLEM: Passage: The gut is generally an almost straight tube supported by the mesenteries (vertical partitions within segments), and ends with the anus on the underside of the pygidium. However, in members of the tube-dwelling family Siboglinidae the gut is blocked by a swollen lining that houses symbiotic bacteria, which can make up 15% of the worms' total weight. The bacteria convert inorganic matter – such as hydrogen sulfide and carbon dioxide from hydrothermal vents, or methane from seeps – to organic matter that feeds themselves and their hosts, while the worms extend their palps into the gas flows to absorb the gases needed by the bacteria. Question: How much of a Siboglinidae's weight is symbiotic bacteria?

SOLUTION: 15%

PROBLEM: Passage: Several dozen radioisotopes have been characterized. 65Zn, which has a half-life of 243.66 days, is the most long-lived radioisotope, followed by 72Zn with a half-life of 46.5 hours. Zinc has 10 nuclear isomers. 69mZn has the longest half-life, 13.76 h. The superscript m indicates a metastable isotope. The nucleus of a metastable isotope is in an excited state and will return to the ground state by emitting a photon in the form of a gamma ray. 61Zn has three excited states and 73Zn has two. The isotopes 65Zn, 71Zn, 77Zn and 78Zn each have only one excited state. Question: What does the superscript "m" indicate?

SOLUTION:
metastable isotope