Presumptuous means failing to observe the limits of what is permitted or appropriate.
Option C is the correct answer because “overconfident “ means being extremely confident without assessing limits, hence it is the correct answer.
Option A is incorrect because “ridiculous” means something that deserving or inviting derision or mockery; absurd.Hence incorrect.
Option B is incorrect because “unthoughtful” means showing little or no concern to people’s needs hence not related to the given word.
Option D is incorrect because “ambiguous” means to be open to more than one interpretation; not having one obvious meaning, hence it is incorrect.