The correct option is C Fastidious
A fastidious person is one who gives too much attention to small details and wanting everything to be correct and perfect. For example, " They were too fastidious to eat in a fast-food restaurant." Hence, Option C is correct. Among the rest of the options, obstinate means,stubbornly refusing to change one's opinion or chosen course of action despite attempts to persuade one to do so, unconquerable means stubbornly refusing to change one's opinion or chosen course of action, despite attempts to persuade one to do so, invincible means too powerful to be defeated or overcome. These options do not express the intended meaning, hence incorrect.