The word "obdurate" is an adjective that describes someone who is stubbornly refusing to change their opinion or course of action. It implies a hardened, unyielding, or intractable nature, often in the face of persuasion or reason. It suggests a strong resistance to influence or change.
Option B, "Stubborn," is the closest synonym. "Stubborn" perfectly captures the essence of "obdurate," referring to someone who is unwilling to change their mind or attitude, even when there are good reasons to do so. Both words convey a sense of inflexibility and resistance.
Option A, "Flexible," is incorrect because it is an antonym of "obdurate," meaning able to be easily modified or adapted. Option C, "Soft," is incorrect; while it can imply pliability, it doesn't relate to mental or emotional resistance in the same way "obdurate" does. Option D, "Transparent," is incorrect as it means clear or easy to understand, which is unrelated to being unyielding.