Read the excerpt from Moon Mission. NASA is inviting its international partners to pitch in. Russia may provide the air-lock module. Japan might contribute an additional module that will assist with propulsion and communications. Canada could build a robotic arm that would allow Gateway to do outdoor work. What is the central idea of the excerpt? Gateway will be difficult to build. NASA is incapable of working alone. Canada builds better robots than other countries. NASA will work with other countries on Gateway.