Natalie often challenges herself to be aware of her own preconceptions and biases, to look for alternative explanations for things, and to actively question statements rather than blindly accept them. Her friends sometimes accurately refer to her as a(n) thinker.

critical thinker              

Explanation:

Critical thinker: The term "critical thinker" is described as a person who generally makes analysis related to different facts in order to establish judgement. However, being critical means that a person is skeptical, rational, makes unbiased analysis, or evaluates factual evidences. A critical thinker makes a reasoned judgement that is often considered as well-thought-out and logical and just not accept any argument rather he or she questions the argument and then make any conclusion.

In the question above, the given statement represents critical thinker.

answer; (d) anthropology;