A、necessary supplies until next April. B、technological support until next April. C、free crew and cargo transportation to the sta

Now that the U. S. space shuttle Discovery is back on Earth, future shuttle missions are postponed until the space agency NASA solves the problem of launch debris endangering the orbiters. Whenever missions resume, they will continue building the International Space Station ,which the United States operates with Russia and the support of Europe, Canada, and Japan. But there is a legal obstacle that may keep U. S. astronauts off the Space Station.
  The issue dates hack to 1996 ,when the two countries agreed that Russia would provide the United States free crew and cargo transportation to the station until next April. This provision proved crucial during the long ban on shuttle flights after the Columbia disaster in 2003 ,for the United States had no other way to get its astronauts and supplies to the station.