What is the best definition for the word "undermine" in the context given?

The term "undermine" refers to the act of weakening or damaging something gradually or in a subtle way. In this context, "challenge" is the most fitting definition because it captures the essence of questioning the strength or validity of something, thereby weakening it. When you undermine an idea or authority, you are effectively challenging its legitimacy or support, leading to potential erosion of trust or stability. This definition aligns well with the implications of the word "undermine," which carries a connotation of covert or gradual erosion rather than an overt attack. The other options do not convey the same sense of subtle destruction or weakening that is inherent in "undermine."