Why Is Saturation Considered a Very Difficult Goal for Qualitative

Why is saturation considered a very difficult goal for qualitative researchers?

A) The world is so complex that data almost never fail to yield new insights.
B) Researchers are limited by time and funding,and cannot always continue collecting data until saturation.
C) Saturation requires a correlation between variables,and many qualitative approaches are not designed to establish correlation.
D) It is very difficult to select cases according to their distinguishing features without introducing bias.