For light to travel across the solar system, it will take ______.

A．become ignorant savages again
B．find the "time barrier" unbearable
C．will not combine solar and stellar space
D．cannot adapt to the abrupt change of scale

A．the development of attitudes is most important
B．people's behavior can be shaped by direct or indirect experience
C．conscious instruction is important in shaping people's behavior
D．unpleasant experience leaves a greater impression on people