A、It takes 20 minutes for a radio signal to travel from Mars to Earth. B、It takes 20 minutes to prepare for communications. C、It

Research subjects who have lived with limited human contact since January recently completed an experiment. The six, four men and two women, lived near the top of a volcano on the Pacific island of Hawaii. They agreed to stay in a small, restricted area as part of a study to learn about the mental and emotional effects of a long-term space mission. The subjects lived and acted much like astronauts would on an eight-month long visit to the planet Mars. Individuals who ace able to deal with long-term space travel need to have special qualities or traits. They need to be able to deal well with isolation and pressure for up to three years on a trip that would take them far from Earth.
    During the experiment, the subjects wore space suits like those worn by astronauts and travelled in teams whenever leaving their living structure. The kinds of foods available to the subjects were limited. They ate mostly freeze-dried or canned food during the experiment. All communications between the “crew mem bersand outsiders were given a 20-minute delay, increasing the sense of isolation. Twenty minutes is the time it takes a radio signal to travel from Mars to Earth.
    In the experiment, researchers used games to study human behaviour. The crew members played games designed to measure their ability to work together. Games also helped measure their ability to deal with pressure or stress. The crew members also kept documentation of how they were feeling. In addition to activities, members of the team wore sensors that measured voice levels and how near they were to others in the living space. Kim Binsted, a professor at the University of Hawaii, was one of the lead investigators in the study. She said the sensors could record if people were avoiding one another or if they were close to each other in an argument. "We’ve learned, for one thing, that conflict, even in the best of teams, is going to arise,“ Binsted said. "So what’s really important is to have a crew that, both as individuals and a group, is able to look at that conflict and come back from it. ”
    Other countries have performed studies on the effects of long-term space flight. The researchers in Hawaii, however, say their project provides an environment most like Mars. The area on Mauna Loa is covered with hard, red volcanic rock. The crew members were required to carry out studies of the rocky surface, make maps and care for their habitat.
    19. How many subjects did the experiment include?
    20. What special qualities should an individual have to travel in space?
    21. Why were the subjects given a 20-minute delay in their communications with outsiders?
    22. What is the difference between the experiment in Hawaii and those in other countries?