所谓专题作业法是以学习和掌握独立的学科知识为目的．而不是以解决实际问题为目的。()

Passage Three

What would happen to some countries if tourism stopped

A．Their economies would be ruined.

B．It would keep their economies going.

C．There would be no more environmental pollution there.

D．People have no chance to travel there.