If There Are Uncertainties in Aspects of an Earth System

If there are uncertainties in aspects of an Earth system, which of the following statements is most true?

A) The scientific method is not helpful for making any policy decisions.
B) This implies a lack of knowledge, and no conclusions can be drawn from what is known about the system.
C) Policy makers should not accept the findings of scientists until they are absolutely certain about their predictions.
D) It is normal for uncertainty to exist in our knowledge of a highly complex and changing system.