单项选择题
In about two years, NASA astronauts will go into space with personal assistants. Robotic assistants, of course. About the size of softballs, these personal satellite assistants (PSAs) can float throughout the space shuttle or space station, automatically monitoring life support systems, snapping photos, and taking over monitoring tasks from failed sensors. They’re equipped with collision avoidance system so they won’t bump into anything Naturally, they’re wireless. Thanks to their videoconferencing capabilities, the PSAs offer a virtual presence for ground crews and scientists, letting them advise astronauts--in real time --in the midst of their experiments. The PSAs. will be stowed until the spacecraft reaches orbit (天体运行的轨道). And then activated by the astronauts, ground crews, or even by the spacecraft itself or other PSAs requesting help, they can work automatically or respond to voice or radio commands, and can exchange information with the spacecraft’s main computers.
Floating through the spacecraft, the little robots will measure gas levels, temperature, and atmosphere pressure--making them ideal for checking alarms and dangerous areas, such as the compartment that caught fire on the Mir space station. And, if "smart" identification tags are added to inventory items like food pouches and experiment samples, project manager Yurt Gawdiak of NASA’s Ames Research Center says PSAs could track inventories.
One of their biggest benefits may be size. By squeezing into hard-to-reach spaces of the shuttle or space station, PSAs can go where no man has gone since the vehicles were first assembled--simply because man doesn’t fit.
A．PSAs can automatically monitor life support systems, snapping photos, and taking overmonitoring tasks from failed sensors.
B．They are capable of videoconferencing so that they offer a virtual presence of ground crows and scientists.
C．They can go where no man has gone since the vehicles were first assembled.
D．All of the above mentioned.