The best title for this passage would be ______. ( )

A．it protects him against the harmful rays from space
B．it provides sufficient light for plant growth
C．it supplies the heat necessary for human survival
D．it screens off the falling meteors

A．their English is not good enough
B．they are afraid they might meet with unfair judgment in these areas
C．there is a wide difference between Asian and Western cultures
D．they know little about American culture and society