______such work before, she asked advice,from many experienced workers and planned everything carefully.

While ______ the gun, the satellite has sent more than four billion bits of information back to earth.A) having orbited B ) being orbitedC) having been orbited D) orbiting

A．People won't use their eyes.
B．In traveling at high speed, eyes become useless.
C．. People can't see anything on his way of travel.
D．People want to sleep during traveling.