造影检查的目的是The purpose of angiography is
A:增加器官或组织的自然密度 Increase the natural density of tissues or organs
B:增加器官组织的自然对比度 Increase the natural contrast of tissues and organs
C:降低器官组织的自然密度 Decrease the natural density of tissues or organs
D:增加器官组织的人工对比度 Decrease the natural contrast of tissues and organs