What is skepticism? a) a new scientific idea b) being interested in new or different ideas c) a general agreement among scientists about a scientific idea d) the understanding that knowledge in a particular area can be uncertain

It is D because skepticism is the doubtfulness of something, most likely a theory. Answer D refers to the knowledge in a particular area can be uncertain. This basically means that whoever is skeptical about that knowledge in that particular area is doubtful that your theory is true.